Warm engine HIGH IDLE!!!

Expert technicians out there, I need your HELP!!! I have had this problem for a long time and just can't find out the cause.

I have a 1995 Civic EX with a B16a. Before the swap, the idle would fluctuate when engine is warm (d16 motor). After the swap, the fluctuating idle is not as noticeable. But this is the problem now...

When I start the car cold, the engine revs up to 2000rpm which is normal for cold start. Everything is fine and slowly, the rpm goes down as the engine warms up! The idle will go down to about 1000rpm! Now, when the car finally warms up and the radiator fan comes on 2 times, the idle is now at 1600rpm. It doesn't fluctuate, it just idles at that rpm.

I turn the idle screw all the way in, and the idle is still at 1200rpm. Interestingly, when I hit the gas padel really quick and let go, it dips down to 900rpm, and then shoots back up to 1600rpm.

I've changed thermostat, ECT Sensor, Radiator fan switch, IAC valve is working, Fast thermal idle valve is working, TPS sensor output voltage within spec, timing is ok, head gasket is ok, . What is the problem? The car runs fine, but the idle is too high! It looks like the engine wants to idle at 900rpm but the ECU is compensating for something by increasing the idle.

Does anybody know what sensor or what item work in controlling the idle after the engine warms up but not when it's cold idling?

Please HELP!!! This has been a problem for 2 years......

Come on, I know there must be some super Honda tech out there that can help me out!!! Does anyone think it might be the FITV? How often does that valve go bad? But if my cold idle is ok... does that mean I can rule out the FITV?

done a vacuum test yet? the vacuum at idle should be at a steady 17-22inhg (take or add 2inhg) at normal operating temps. check voltage on the MAP sensor yet?

yes, vacuum is good and MAP sensor is good. I don't think it's these 2 things because the car cold starts fine. Any other things come to mind???