I have a '86 TPI system and the throttle will sometimes hang open just a little. Without the engine running the throttle rolls fine always going back to the set screw. While running (either at idle or driving)if you hit the gas pedal the throttle will not come all the way back to the set screw causing a high idle.You either have to roll it back by hand or tap the pedal. I checked the cable and its fine.Also no carbon or anything in the throttle body.
Could it be the throttle position sensor? graemlins/clonk.gif

take off the throttle cable and snap the butterflies a couple of times if dragging try this...make sure the butterflies are tight on the shaft (tighten them while the throttle is closed) if still no luck check the voltage on the tps before loosing and check for drag there...hope this helps

To me it does sound like the TPS sensor. You may also want to clean out the throttle body. If you clean out the throttle body make sure you use fuel injector approved cleaner.