Stuck Throttle

I have a 1998 RAV4 (4WD, 4 Door). Yesterday while driving at highway speeds the engine began exhibiting what appears to be a stuck throttle if I rev beyond 3000 RPM.

I don't think the throttle butterfly or the cable is actually sticking because the butterfly appears to return to the idle position when I release the gas pedal.

Hence, I suspect a vacuum leak or something similar.

I'm going to read codes out this weekend.

In the meantime, can anyone advice me on what they think the problem may be?

Thanks

Jeff

On my Rav 4 the throttle stick at idle if I don't keep the throttle body clean. About every 5000 miles I take off the intake boot and take a rag with a little carb cleaner on it and clean all around the butterfly valve with the valve open. Reach way in there and clean out all that crud, works fine then..

Having a problem with the idle going up too. It tripped a code in the ECU. How do i get the codes from there??? Can i jumper something or is there a way to find out the codes without going to a dealer????