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      09-14-2011, 10:28 AM   #15
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ken1137's Avatar

Drives: a slow 2009 e90 335i
Join Date: Jun 2011
Location: Chicago

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2009 e90 335i  [3.20]
Originally Posted by startover View Post
I'm planning to go for the software only tune on my 135i (likely a reflash via cobb or evolve-R, no piggy backs). I'm not willing to add any other bolt ons such as exhausts/DP's, and I don't want to add an intercooler either so the car will look 100% stock.

My question is are there certain things I can do to improve the odds of the car running stable after the tune, given that I'll be using a non-aggressive map? I absolutely hate the idea of engine errors/overheating/limp modes/HPFP failures etc.

The car currently has about 20k miles on it. I read it somewhere that it's recommended to replace spark plugs at this stage to make the tune work better. I'll likely also change the air filter (OEM, or is a drop-in worth it?). Will do an oil change too.

What else would you recommend?
I had some of the same is what I recommend based on my research:

1) Cobb A/P - upside is tremendous as Cobb's technology expands.
2) FMIC upgrade - required due to heatsoak, higher psi with tune.
3) Recirculation valve upgrade - wider range of boost pressure, more reliable than the OEM valves
4) Berk axle back

I did not change my down pipes or mid pipes due to potential error codes but mainly emissions. I did not get a definitive answer regarding the IL State Emissions. That said, sounds like the N55 has no cats in the mid pipe (?) So, maybe Berk resonated mid pipes in the future but I did change to Berk Street Performance axle back.

Air filter ...just used the existing box and purchased an aFe drop in filter. This will start a debate but from what I read and heard there is no need to mod the air filter since the hP gain is minimal if anything at all.

I did consider upgrading or adding another oil cooler but I'm not going to track the car so to my understanding I can skip this mod.

Have fun and good luck.

BMWCCA member

Last edited by ken1137; 09-14-2011 at 11:00 AM. Reason: correction