2000 Impala throttle issue

Hi. New here. Great spot.
I have an issue with my 2000 Impala. (Close to 100,000 mi.)
When driving a distance and at hwy speeds for more than about 30 min., I find that when I must slow to a stop (say at a toll booth) the throttle will "stick" and the engine will revv very high. If I were to shift to park or neutral, it would race beyond what I consider safe limits!
It only does this occasionally and of course never when a tech is checking it out, and once turned off and restarted after a few minutes, will resume to normal operation. It may stick again down the road after some travel at hwy speeds, but not every time.
I have had the fuel system "cleaned" etc. and a small vac. leak fixed in the past.
There has never been any warning light when it does this.
Is this the Throttle position sensor "sticking"?
Any help is MUCH appreciated.

Mark

remove the throttle body, remove the mass air flow sensor from the TB, remove the idle air contro valve from the tB. Clean all the gunk off the throttle blade and idle air passage. Reinstall everything...

Thanks! I will give it a shot ASAP.
Mark