If you ride a Milwaukee-Eight powered Harley, whether it is a Street Glide, Road King, Fat Bob, or a Softail, a 2-into-1 exhaust is among the most effective upgrades you can bolt on. Merging both head pipes into a single collector and muffler builds scavenging that the stock dual system simply cannot match, which usually means a fatter midrange and a deeper, more focused exhaust note. The catch is that a 2-into-1 changes the air-fuel demand of the engine, so the best results come when you pair it with a tune.
We spent time with the most popular 2-into-1 systems for the M8 platform, listening to them at idle and under load, checking fitment against bags and floorboards, and noting which ones actually need a heat shield rewrap or a dyno session to behave. Below are our seven favorites, ranked best first, with honest notes on sound, build quality, and what each one does well and where it falls short.
| Photo | Product | Score | Buy |
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Vance & Hines Hi-Output 2-into-1 Exhaust Best Overall Full system, stepped 2-into-1 collector, slip-on style muffler, fits M8 Softail and touring applications |
9.5 | 🛒 Check Price |
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Bassani Road Rage 3 2-into-1 Exhaust Loudest and Meanest Megaphone style 2-into-1, short or long versions, hand-built stainless and steel construction |
9.3 | 🛒 Check Price |
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S&S Cycle 2-into-1 50 State Exhaust Best Engineered 2-into-1 with merge collector, 50-state legal version available, M8 touring and Softail fitments |
9.2 | 🛒 Check Price |
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Rinehart Racing 2-into-1 Exhaust Best Balanced Tone 2-into-1 full system, multiple end cap and finish options, M8 bagger and Softail fitments |
9.0 | 🛒 Check Price |
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Two Brothers Racing Comp-S 2-into-1 Exhaust Best Lightweight 2-into-1 with carbon fiber end cap, stainless construction, M8 Softail and touring versions |
8.8 | 🛒 Check Price |
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D&D Billet Cat 2-into-1 Exhaust Best Torque Builder 2-into-1 with billet end cap, tunable baffle options, M8 touring and Softail fitments |
8.6 | 🛒 Check Price |
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Trask Performance Assault 2-into-1 Exhaust Best for Big Power Builds 2-into-1 with large diameter collector, stainless construction, M8 touring and Softail fitments |
8.4 | 🛒 Check Price |
1. Vance & Hines Hi-Output 2-into-1 Exhaust: Best Overall
The Vance & Hines Hi-Output is the system we kept coming back to. On the Milwaukee-Eight the stepped collector does exactly what a good 2-into-1 should, it fills in the midrange so the bike pulls harder out of corners and rolls on with real authority instead of just getting louder. The note is deep and purposeful, more rumble than rasp, and it does not turn into an ear-fatiguing drone at highway speed, which matters if you actually log miles.
The honest weakness is that this is not a bolt-on-and-forget part. Without a Fuelpak or a flash tune the bike will run lean, you will feel a flat spot off idle, and the headers will blue faster. Budget for tuning as part of the install. The heat shields cover well but the right leg still picks up heat in slow traffic, which is a trait of nearly every 2-into-1 on this platform rather than a fault unique to this pipe.
- Stepped header design tuned to broaden Milwaukee-Eight midrange torque
- Full coverage heat shields reduce bluing and rider leg heat
- Tunable with the Vance & Hines Fuelpak or any M8 flash tuner
Pros: Strong, usable torque gain right where street riders want it; Aggressive but not droning sound at cruise; Proven brand support and easy tuner pairing
Cons: Requires a tune to run correctly and avoid hesitation; Heat shield coverage still leaves some warmth to the right leg
2. Bassani Road Rage 3 2-into-1 Exhaust: Loudest and Meanest
If your priority is sound, the Bassani Road Rage 3 is hard to beat. The megaphone collector gives this system a low, snapping bark at idle and a serious roar when you open the throttle. Build quality is a clear step up, the welds are clean and the finish options, especially the black ceramic, hold up well to the heat a 2-into-1 throws off. On the dyno it makes power across the band, with a satisfying surge up top that the stock pipes never had.
The flip side of all that character is volume. This is a loud system, and after a long day in the saddle some riders find it tiring, plus it will draw attention you may not always want. It also really wants a complete package, a high-flow intake and a proper tune, to deliver its best numbers. Run it bone stock with just an ECM flash and you are leaving performance on the table.
- Megaphone collector delivers an unmistakable deep bark
- Available in multiple finishes including black ceramic and chrome
- Hand-welded construction with quality fit and finish
Pros: A very aggressive sounds available for the M8; Noticeable top-end and midrange pull; Premium build quality you can see in the welds
Cons: Genuinely loud, too much for some neighborhoods; Needs a tune and benefits from a high-flow air cleaner
3. S&S Cycle 2-into-1 50 State Exhaust: Best Engineered
S&S has put serious development into this 2-into-1 and it shows in how the bike behaves. The merge collector is designed rather than just fabricated, and the result is smooth, linear torque that makes the Milwaukee-Eight feel bigger than it is. We appreciated that S&S offers a 50-state legal version, which is rare in this category and a genuine lifesaver if you live somewhere with tough inspection rules.
The trade-off with the compliant version is that it is noticeably more reserved in tone. Riders chasing maximum noise will find it polite. Even the standard version is more refined than rowdy, so this is the pick for someone who wants performance and a quality sound without rattling windows. As with every system here, you will get the most out of it with a tune, even though it is more forgiving than most if you delay that step.
- Engineered merge collector for clean scavenging and torque
- 50-state legal option for emissions compliant riders
- Backed by S&S engineering and dyno development
Pros: Real, repeatable power gains documented by S&S; Emissions legal version keeps it street safe in strict states; Refined sound that is aggressive without being obnoxious
Cons: The 50-state legal version is quieter than some riders expect; Tuning still recommended for the strongest results
4. Rinehart Racing 2-into-1 Exhaust: Best Balanced Tone
Rinehart built its reputation on sound, and this 2-into-1 carries that DNA. Where some systems chase raw volume, the Rinehart goes for a rich, rounded tone that fills out beautifully off idle and never crosses into the tinny rasp cheaper pipes produce. On a Street Glide or Road Glide it looks like it belongs, with clean shielding and finish quality that holds up. Midrange pull is a clear step over the factory dual setup.
If you are chasing the absolute biggest dyno number, this is not quite the leader, it trades a sliver of peak output for a more refined character. The other small catch is that the sound depends on which end cap you run, so it is worth researching the options before ordering rather than assuming the default cap gives the tone you heard in a video.
- Tuned to a rich, full exhaust note without harsh drone
- Interchangeable end caps to fine tune sound and look
- Chrome and black finishes with quality heat shielding
Pros: Excellent, warm tone many riders prefer over rivals; Looks clean and integrated on baggers; Solid midrange improvement over stock
Cons: Power gains are good but not class-leading; Best sound requires choosing the right end cap
5. Two Brothers Racing Comp-S 2-into-1 Exhaust: Best Lightweight
The Two Brothers Comp-S brings a sportbike sensibility to the Milwaukee-Eight. The carbon fiber end cap is not just for looks, it shaves weight off the tail of the bike, and the compact muffler design keeps clearance generous around saddlebags and floorboards. The sound is deep and throaty with crisp throttle response, and the stainless build feels durable. For riders who want a leaner, more modern aesthetic than chrome megaphones, this is the standout.
Two honest notes. The carbon cap, while striking when new, can pick up some heat discoloration after a season of hard riding, so it asks for a little care. And like every aggressive 2-into-1 on this engine, it really needs a proper tune, run it without one and you will get popping on deceleration and a lean stumble that masks what the pipe can actually do.
- Carbon fiber end cap trims weight and adds a race look
- Stainless construction with a deep, throaty output
- Compact muffler keeps lean angle and bag clearance
Pros: Light and good looking with the carbon cap; Aggressive sound with strong throttle response; Compact design clears bags and boards well
Cons: Carbon cap can show heat discoloration over time; Definitely needs a tune to run clean
6. D&D Billet Cat 2-into-1 Exhaust: Best Torque Builder
D&D has long been a torque-focused brand, and the Billet Cat 2-into-1 leans into that. This system is tuned to build low-end and midrange grunt, which is exactly what a loaded touring bike or a heavy Softail wants when you roll on from a stop. The billet machined end cap looks the part and the changeable baffle options are a genuinely useful feature, letting you dial volume up or down without buying a whole new muffler.
The honest drawbacks are fitment and top-end. On certain Softail variants the install can take some fiddling to get bag and bracket clearance right, so read the model notes carefully. And because the tuning priority is low and mid, it does not pull as hard up top as the megaphone systems. If your riding is mostly canyon-carving at high RPM, look elsewhere, but for real-world street and highway torque it delivers.
- Designed around low-end and midrange torque for cruising
- Billet machined end cap with multiple style choices
- Changeable baffles let you adjust volume and flow
Pros: Strong bottom-end grunt that suits heavy baggers; Quality billet hardware and finish; Adjustable baffles for sound and flow control
Cons: Fitment can be fussy on some Softail models; Less peak top-end than megaphone style rivals
7. Trask Performance Assault 2-into-1 Exhaust: Best for Big Power Builds
Trask aims its Assault 2-into-1 at riders building serious power. The larger diameter collector is sized to flow for cammed engines, big bore kits, and even forced induction setups, which is where this pipe earns its keep. The stainless build handles the extra heat those combinations produce, and the sound is appropriately race-inspired and deep. If your M8 is more than a bolt-on bike, this is the system designed for your level.
That same flow capacity is the catch on a stock or lightly modified engine. Sized for big power, it can soften the very low-end response on an unmodified M8, so a baseline bike may actually feel happier with a more torque-tuned pipe from earlier in this list. It is also loud and absolutely demands a custom dyno tune to realize its potential. Match it to the right build and it shines, bolt it to a stock bike and it is more than you need.
- Large diameter collector flows well for built engines
- Stainless construction stands up to high heat
- Aggressive styling that suits performance builds
Pros: Flows enough to support cammed and big bore M8 builds; Tough stainless construction; Deep, race-inspired sound
Cons: Overkill flow can soften low-end on a stock engine; Loud and firmly needs a custom dyno tune
Frequently Asked Questions
Do I need a tuner with a 2-into-1 exhaust on a Milwaukee-Eight?
Yes, in almost every case. A 2-into-1 changes how much air the engine flows, and the factory fuel map cannot keep up with that change. Running a new exhaust without a tune leaves the engine lean, which shows up as a hesitation or flat spot off idle, popping on deceleration, extra heat, and faster header bluing. A Fuelpak, a Power Vision, a Thundermax, or a custom dyno tune restores the correct air-fuel ratio and lets the pipe actually make the power it is capable of. Treat the tune as part of the exhaust install, not an optional extra.
Is a 2-into-1 better than 2-into-2 dual exhaust on an M8?
For performance, a well-designed 2-into-1 usually wins. Merging both cylinders into a single collector creates a scavenging effect that pulls exhaust out more efficiently, which typically builds a stronger and broader midrange than a dual system. A 2-into-1 also tends to be lighter and centralizes mass. Duals can look more traditional and some riders prefer the symmetrical staggered style, but if your goal is torque and throttle response, the 2-into-1 is the proven path on the Milwaukee-Eight platform.
Will a 2-into-1 exhaust make my Milwaukee-Eight run hotter?
Some added heat near the collector is normal because both head pipes now merge in one area, and if the bike is running lean from a missing tune it will run hotter still. The good news is that a proper tune brings fueling back to spec and keeps temperatures reasonable, and most quality systems include full heat shields. You can further reduce right-leg heat with exhaust wrap or aftermarket shields. In stop-and-go traffic almost every M8 with a 2-into-1 radiates some warmth, so this is a platform trait rather than a flaw of any single pipe.
Are these 2-into-1 systems legal for street use?
It depends on the system and where you live. Most performance 2-into-1 exhausts are sold for closed-course or off-road use and remove the catalytic converter, which is not emissions legal in strict states like California. A few options, such as the S&S 50-state legal version, are designed to pass emissions and keep you compliant. If you live somewhere with vehicle inspections or strict noise enforcement, check for a 50-state legal or CARB compliant version before buying, and be aware that the legal versions are usually quieter.
How much power does a 2-into-1 exhaust add to a Milwaukee-Eight?
On its own with a tune, a quality 2-into-1 typically adds a handful of horsepower and, more importantly, a meaningful bump in torque through the midrange where you actually ride. The gains grow substantially when the exhaust is part of a complete package with a high-flow air cleaner and a proper tune, often called a stage one upgrade. Add cams or a big bore kit and a flow-oriented system like the Trask can support much larger numbers. The exact figures vary by model, baffle choice, and tune, so treat published numbers as a guide rather than a guarantee.
Our Verdict
For most Milwaukee-Eight riders the Vance & Hines Hi-Output 2-into-1 is our top pick, it delivers the strong, usable midrange torque street riders actually feel, a deep tone that does not drone on the highway, and easy tuning support through the Fuelpak ecosystem. Our runner up is the Bassani Road Rage 3 for anyone who puts sound and aggressive top-end character first, just be ready for serious volume and the need for a full intake and tune package. Whichever you choose, plan for a tune up front and you will get the gains and the bark the M8 platform is capable of.
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