Sounds to me like your throttle plate is sticking open. If the TPS was still reporting partial throttle when the throttle was closed, the ECU would dump too much fuel, and the engine would probably bog down instead of rev high. The actual throttle body would be closed, not allowing enough air for proper combustion of the gas.
You should be able to duplicate this at a stop, with the engine off... Open the hood, and try holding the gas pedal at the height you would normally have it at, for about 15-20 seconds or so, then release. If you don't immediately see the throttle linkage move back to the closed position, something is up.
Now, the TPS could be failing in such a way that it hold the throttle plate open, but I'm not sure how likely this would be. Look for:
broken/missing/weak springs on the TB and throttle plate assemblies
sticky accelerator cable
dirty TB (caked up gunk around the throttle plate holding it open.
possible interference from the cruise control system