Ir is the IAC(idle air control) Valve that was replaced, yes that could cause similar problem.
When you push the clutch in you remove the load from the engine, so assuming there was a load then RPM would increase if throttle plate didn't close.
I would first test for mechanical issue with throttle plate and linkage.
Throttle has a spring on it so it can close against the air stream the engine is pulling in.
If spring breaks then throttle plate is very slow to close.
Remove gas pedal cable and cruise cable from throttle linkage.
Open throttle and let it snap closed
Run RPMs up to 2,000rpm and hold it there, then release, it should snap closed.
If there is any delay or slowness then you make have a bad spring, OR........throttle could be sticky from build up in throttle body, may need to pull it and clean it.
Pull and push on the gas pedal cable and cruise cable, both should slide in and out easily, you can lube these with spray lube, sticky cable can hold throttle open.
TPS(throttle position sensor) is on the opposite side of the throttle plate from the cables/linkage.
This tells the computer if you want to go faster or slow down.
This can be tested with a voltmeter or OHM meter.