so you've checked the vacuum pipe that goes from the inlet manifold to the ecu. mine perished the otherside of the bulkhead just before the ecu and was doing exactly what you're describing. you can't see it unless you remove the scuttle panel.
oki now my car keeps geting stuck at 2.000 rpm i just drove :|
i noticed the pedal moves up and has alot of play init the cable could be sticking isit easy to change]