so my car was running a little rough. the engine was shaking slightly and the exhaust from the muffler was coming out in puffs, rather than a smooth continuous flow. my mechanic said change the ignition coils and spark plugs so i did all 6. nothing changed. what else could cause this problem? btw the car hasnt lost any power. the acceleration is normal and it starts as normal.

maby a vacuum leak

i dont really know anything about vacuum leaks. do you have any DIY tips?

is the CEL on? Have you done any maintanence? We need more info.

Try a stomp test.

http://www.bmwe34.net/e34main/Trouble/Engine_codes.htm

Try searching "rough idle" on this forum for ideas too.