Passat Runaway Revs

My 1990 Passat 1.8 CL has developed an intermittent runaway rev problem. First time out in the morning is no problem, but park for 15 minutes and drive again and the revs just take off, clutch out (5sp manual) and the motor goes to maybe 4000 rpm. Stomping the gas pedal works to bring it down maybe once out of 5 times, otherwise it returnes to normal after switching off and restarting. I see there is a bit of gas leaking from around the top of the carb housing - otherwise could it be a dirty throttle body? VW dealer can't help without the problem being present when I'm at the shop. Anyone have any idea?
Thanks, Bob in Denmark

Kinda had the same problem with my 96 5 speed. could be two things that i found out. Could be a vac problem.....i changed the tube from the air fliter to the throttle and that helped for a couple thousand miles.....second thing is check the cluch.....i found that before mine went i would romp on the gas rpms would go up but no movement till it hit 6.5.....but i would say have the vac seals checked out