A couple of tests...

1. Measure the voltage at the two wires going to the idle control valve. Is the voltage slowly changing along with the idle? Or voltage staying the same/no correlation to changing idle, yet idle increases anyway? That can rule out the electronic Idle Control Unit and the various inputs going into it.

2. I made an idle control valve bypass hose out of heater hose and garden sprinkler fittings found at a hardware store. Then connected that in place of the Idle Control Valve. Use vice grips to squish the hose in the center to only allow a little air through. Start the car then adjust to what the idle should be. Let car warm up and see if idle remains the same and/or if you can adjust it after warm to be the correct idle. This would eliminate air leaks elsewhere - if maintains idle, then it is possible for the Idle Control Valve also to keep the idle at what it should be.