Rough idling on my 93 300E

My 300E idles rough in gear when you come to a stop n go situation. It smoothens as you take off. The dealer replaced the voltage regulator($296) but that didn't stop it. Its odd coz the whole car shakes. It also does it whether the engine is hot or cold. A year ago, the M16 motor and the air mass sensor was replaced. Cost me a ton then. Any suggestions anyone. Please help.