the engine in my 1986 528e is a transplant . graphted in this week . I also had the transmission rebuilt this week it is the first time i've ever seen the car run. the exhaust system was replaced with one from a 2001 passat after alot of creative thinking and fabrication. The car ran like a dream most of the way home but.... towards the last couple of miles the engine started surging under acceleration it was as if i were steping on the gas and immediately letting up even though i wasnt. has any of you ever ran into this problem or know anyone who has ? please post if you have any feedback or helpful information.