PeachParts Mercedes-Benz Forum - C220 1994 rough idle and no power between 700-1500RPM

I have Benz C220 1994 model. Most times the car runs smoothly although at times at idling the revs keep jumping up between 700-1000. Also at that time if I shift to drive, and step on the brakes, the car feels as though it is about to take off. If I release the brakes the car will shoot off and gain speed. At normal times this would not happen. Also at times between 700-1500RPM the car shudders and has no power. Once it crosses 1500RPM, the car is back to normal. The throttle accuator used to make a clicking noise on ignition and I was adviced to change it. I have changed it and the noise has gone but the problem still lives. Also the wiring harness has been repaired previously. What could the problem be? ALso do I need to take some precautions when changing the accuator?
Help!!!