[Blown 330]

Got the service engine soon light today, went to my friends shop and scanned the computer and it came back as misfires on cylinders 2, 4, 5, and 6. When looking at the event data it appears the misfires occurred at idle (~700 rpms) and just when started (60 sec runtime). Now my local BMW will not touch the car because of muffler delete, even called another dealer and they also refused to touch it. This is not the first time I have had this problem, just the first time i scanned it myself (3rd time in the past 2 months). BMW contines to blame this problem on a lack of back pressure due to having no mufflers (I know that is a load of crap). What else could be causing these misfires?