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      11-21-2012, 04:01 PM   #7

Drives: E90
Join Date: Feb 2012
Location: Orange County

Posts: 510
iTrader: (0)

i had the same issue with my jb4.. EXACTLY. I would describe it as a shudder during shifting. I first thought it was tranmission but then found out most of the time it is old spark plugs. not being able to deliver the precision needed during heavy shifts, believe it or not. read many accounts of this. since have gone back to stock but just FYI i am pretty sure i know the issue.