[Naumansheikh]

I just bought a 2025 BMW M4 Competition. For tuners out there, what’s a few first mods that don’t cost an arm and a leg but add real horsepower right off the bat, also remove that 158 mph governor, and give a deeper sound without turning into a two-stroke lawnmower or droney highway buzz?

- Catted downpipes + intake?
- Catless for max flow/sound?
- Midpipes only (resonated vs non-res)?
- Tune-first then pipes?

Not super deep into tuning yet, so I’d really appreciate all your answers.

Thanks!

[G80SWFL]

From the videos ive seen online the IRL modular V2 midpipe with valve controller is deep and no rasp

[TopJimmy]

You said “real horsepower”, and that takes a tune. This platform already has 500HP so bolt ons don’t feel like anything, they just change sound.

I recommend you start with a DME unlock and the “Stage 2 MultiMap FlexFuel” tune that comes with Bootmod3. This is a mod you will surely feel as a power gain.

If you live in areas with E85 then your mod #2 is a flex-fuel kit, so you can easily run ethanol mixes with your Stage 2 maps. It’s another feel-able increase when you go from pump gas to E30 or E50.

For sound you said “no lawnmower or rice” so that means deeper is better. Forget catless downpipes, they allow rasp through. Sport cats do very little. Stock cats flow great up to 800WHP so keep them. A single midpipe will deepen your tone. Take the 3.5” resonated MAD midpipe because it doesn’t drone like the 4 and 4.5”. The 3.5” keeps some flow velocity and seems to avoid drone. If you do change DPs later at least there’s a resonator to deaden rasp. Add a MAD Essentials valve controller for easy switching from Stock to Loud when you want. Keep your rear section exhaust (the stick muffler) because it also combats drone. In OEM mode I can drive by church and not be noticed.

If later on you do want diwnpipes, I suggest the ARM resonated so they can also help to deaden down rasp.

[TJay74]

24 M4xC owner here. Without tuning the options are limited that will provide any real gains, but these suggestions have been proven recently.

- AMS intake kit, proven gains with recent independent dyno testing with and without tuning changes.

- MAD secondary cat delete with a valve controller as well. This will give you a nice deep tone and not allow any drone. You will need to code out the ASD for the best results. Nice thing is coding out ASD will also improve the sound quality of the stereo.

- Full CS coding package from Chris3g or Kubah, this will give you a nice 25hp bump in power and raise the limiter to 188mph and improve handling, braking, suspension and how the xDrive system responds.

- Add in a Fuel-It ethanol sensor kit (if you have E85 availible). For now I am using this until I got the unlock and tune route later this year. The stock tuning can handle up to E30 with no issue. Just going from the crap 91 octane I have locally to E20 was worth 2 tenths in the 1/4 mile on my M4. At the time I put me at a 11.02 @ 128 in the 1/4 mile. Now that I added the M2 CS DME coding to my car I need to run the car again as it feels like it has gain some more power for sure and should be able to dip into the 10's.

That should keep you happy for a bit until you decide to tune, once you tune these M4's become animals that rival pretty much anything on the road including some supercars.

Sam Barros (big name in the Nissan GT-R world) did a whole series on his M3xC from bone stock to full bolts on and how the power gains changed. 700whp on the stock DP is easy to hit and will drop the car into the low 10's to high 9's in the 1/4 mile.

[nastynate06]

Isn't "ricer" a racist statement in 2026?

[mike@x-ph.com]

Your first mod should not be a power upgrade; it should be an oil-cooler guard, a midpipe, and a valve controller.

if you want more sound, invest in high-flow catted downpipes

as for the rest, you need a flash tune, i recommend bootmod3. now that it can be done in the US, its a no brainer