Hi My mechanic is stummped. I have an 1981 VW Rabbit pickup with a 1986(?) golf non turbo diesel engine. My problem happens only at higher revs. I can feel a vibration on the gas pedal and the truck seems to speed up or rev up on its own. All moter mounts are new. If sitting still in neutral and I push on the gas slowly the engine will rev up corresponding to the push on the gas then all of a sudden it seems to take off and rev up on its own. By letting go of the gas the engine slows down normally. My mechanic has checked the timing a couple of times and all seems normal. Any ideas would be appreciated. Thanks...G.D.