300CE Missing / Rough Idle - CPS ???

[CE4me]

My 300 CE just developed this miss / erratic idle. After making sure I just did'nt get some bad gas etc. I'm getting ready to take a look at it and wanted some opinions:

Idle (around 600 or so) has a very steady miss / shake. When you start out, I get a sputter, then it smooths out and runs fine (Better than fine actually) I did a tune up about 2 months back so it has Cap, rotor, wires and plugs. (all OEM stuff - not aftermarket parts)

If you raise the idle (with the gas pedal) to 800 rpm or more, the miss is gone. On the highway, the car runs like a million dollars with no problems at all.

It seems like a CPS problem but since I'm not too familiar with the MB, I wanted to get some input. I have the service manuals here with me. ANyone had the same problem? I drove the car appx 35 miles, stopped for a family get together (about 4 hours) and it started doing this immediately after starting it for the ride home.

Thanks for the input

Brian