<VV> Run-on engine

[RB]

Hi!  I have a recent problem with my 1965 140hp 4-speed Corsa which may literally drive me up a wall.  Occasionally between shifts, the engine will accelerate on its own, quickly heading for the redline.  My only way to counter this is to quickly switch off the ignition, stay in neutral, and coast side of the road.  If on a highway, once the engine stops I can blip the gas pedal (which seems to clear up the "jam") and then restart the engine; once restarted, everything seems normal again.  
I've spent days inspecting the topside linkage and the carpets but could find nothing that appeared to bind, even at full throttle.  I even added a small collar on the sloppy cross bar link to keep it from shifting side to side and replaced the return spring.  After the mods I drove the Corsa about sixty miles without an incident. The next day I didn't go two miles before the engine acted up again.  This car is making me a nervous wreak!
Before this problem I had the right-side primary carburetor rebuilt, as the idle wouldn't hold and eventually the engine would stall.  Not being an carb expert, I don't know if anything could be incorrectly installed in the carb causing a run-on condition.  Unfortunately I'm not able to check the linkages under the car, so I can't tell if there's a problem there. I could use the group's guidance; if I take the car to a mechanic with a lift, I'd like to be able to give them something to look for.  As most of you know it's hard to find Corvair- knowledgeable mechanics.  Help!
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