HI Guys,
Jim, I don't have "Check Engine" light on at all. The spark plugs and wire sets were replaced. I had to replace the head gasket because there was this white smoke coming out of the pipe one day, it scared me to death. After that, this slight rough idle occured.

I drove to Tarzana today (very far, traffic bad), and yes the shop is closed. I should have checked the forum for your postings. However, I found a place near my house, Glendale German Motors, specializing in MB. He seems to be reasonable, has 35 yrs of experience. I have an appointment for Tues. next week. I will try this shop for now unless anyone of you out there had a bad experience with this shop.

Wish me luck...