Brought my car to a mercedes repair shop (the one who did the oil seals, see first post). I originally planned on buying an OVP from them (guessing it might solve the problem) but decided first to have one of their mechanics look at the throttle plate. He tried to remove the connectors to the idle control valve and the plate stopped moving, then he reconnected it back. The throttle plate erratically moved again. Then he disconnected the OVP, the throttle plate stopped moving again. Then he reconnected it back and again it opened and closed repeatedly.

Swapped the old OVP with a new one and that did not solve the problem. They don't know how to check the ICV and no stock is available that they can use to test if the ICV is bad.

This is really driving me nuts....