Lets get right to the point...2000 Audi A6 2.7T 75k miles.....Car wont start at times..when it starts it runs at low RPMs shakes really bad and eventually shuts off byitself..and i can smell rich GAS and i see smoke coming under the hood and exhaust...this only happens sometimes...other days it starts fine no rich gas smell..its like nothing happened...any idea what im dealing with here???

 

Coil packs.

 

Do audi's use PVC valves or breather pipe from engine to inlet manifold, if they do i'dsay that the prob. do net search and you will see what i mean. air pressure inside engine not getting out and it's pressurizing, it will cause lumpyness and gassy smell from engine area. it caused by gasses passing through piston rings into bottom of engine gasses go to top of engine and out through breather/PCV valve back into inlet manifold.
worth checking out, simple to do and prob not cost a penny to sort