'91 300se rough idle
 

I am researching the dreaded roughg idle issue that so many people seem to have. While tinkering with mine I switched off the fuel pump at the MAS, removed the air filter housing to get at the fuel dietributer. I turned the key on and there is a growling sound coming from the fuel distributer/EHA area that I can't pin down. It lasts about as long as my rough idle on start up. Not sure if there is any connection but does anyone know what this sound is ? It sounds like a jittery electric motor (similar to a rapidly fluctuating radio control servo) or a small electric motor with really bad bearings.

I disconnected the ICV, MAF pot, and EHA connectors and no change.....