I have run into a few different m3s in North GA that have after market exhaust. I cannot tell what else though. I would figure that the exhaust is the most expensive part and assume the intake and ecu was also done. I have pulled away from lights, roll ons and highway roll ons from about 60 mph or so. Most of the time I got a smile, thumb up, and a shake of the head like "what's in there". I really like them and have a friend who has a stage 3? and he is afraid of my car!! Enough said!!