I bought my 08' with 54k miles on it less then two months ago. Installed the JB4 and I instantly started getting misfire codes for cylinders 3, 4, and multiple cylinders that same day. I have since changed the plugs and moved the coils around with no luck. I'm still getting misfires on 3 and occasionally 4 and 1.
The problem happens almost ALL the time at part throttle (75% max) from 2k - 5k rpm and the car stutters/shakes and starts running rough until I re-start the car. It's gotten to the point that it even happens on map 0 now
But the strange part is, that if I just hammer down the gas pedal, most of the time it will run like a raped ape to redline with no misfires! But anything in-between 2k and 5k rpm accelerating moderately (which is most of my daily spirited driving) it misfires bad
Anyway, I called the BMW dealer I bought the car from (the car was originally bought, serviced, and traded back in from this dealer) and set up an appointment to have them look at it. I gave them the VIN and supposedly the recalls were done already and the HPFP was replaced sometime in 2010 and the injectors in Jan 2011... And of course the OEM warranty was up when I bought the car, but I'm still under the dealers 60 day used car warranty. So I'm hoping they find some bad injectors or coils and fix it for me!
This just sucks... so now I'm pulling out the JB4 and putting the car back to stock tonight, and leaving the SES light on with the 3 misfire codes still showing.