I see someone mentioned the OVP, even if replaced it could be faulty. I had two fail in a year on my 300E.

What is the cold idle ? What is the hot idle ?

If the cold idle is low (500RPM) and hot idle is around 1000RPM, this could be the OVP.

Another trick I use, is when the engine is cold, unplug the OVP, there should be a noticable change in idle, if there is no discernable difference, then its probably no good.