I really like the people at Import Specialists here in Springfield, MO. They have a mechanic named Dave Shipman that has been working on Mercedes for over 25 years.

He hooked the car up to an electronic tester computer (don't know the exact name) but his first incilination was that there was a vacuum leak somewhere.

The car had try to compensate for the problem by adjusting itself, so the adjustments had to be reset. He finally found it by spraying something around the vacuum lines while the engine was running. When spraying near the intake manifold he found the problem.

The gasket needs replaced on the intake manifold. The part is $7 and the labor is $450.

I haven't had him fix it yet. I hope this may help others.