hello all. my problem is that i have a 1996 740il (pre-ausil) that i am having some problems with. i had the motor rebuild about 1200-1500 miles ago and now the car seems like its down on power every once in awhile. took it to a european repair shop here and was told that one of my cat. conv. is clogged therefore causing my car to run on 6 cyl. i was also told that the previous owner rigged the check engine light to somehow not come on and thats why this problem did not set the light. is any of this plausible? i would like to know before i put more money into this vehicle.

ghead thanks in advance