Musta spelt wrong. If its the M111 model, then Yes I would agree it could be the wiring loom as I had a simular issue with my c200. The whole loom had to be replaced.

Other culprits may include the throttle ACTUATOR

The throttle actuator is bassically the black unit on the back of the throttle body. Black plastic, rectangle. The whole body has to be brought. Ive heard of this being faulty, testing fine, and not throwing any faults out. Be aware that the lead comeing from this unit is prone to faliure just like the wiring loom. If you can verify that the donor car was working fine with the used part in it, then by all means go second hand, but if theres no way of verifying its in working order dont touch it! Symtoms Ive heard of include surging RPM, Hesitation, incorrect idle.

I recall the Over voltage relay had issues on these models but i cant recall the symtoms - I think this is rulled out because the m111 models were full electronic injection, IE if this failed the car wont run - any one verify this?