Ok, I thought I was chasing vacuum leak. I checked with propane (yes this works) and found none.

Simptom is when hot I can screw throttle body adjustment screw all the way in to have idle at ~ 800-900. needless to say it won't idle before its' hot set like this.

So if you set idle for the 2-10 min warmup time at ~ 900, it idles at ~ 1500 to 1700 when hot.

Checked air box. Ohm readings are good, flapper moves fine. looks very good.

aux air regulator is also good.

What do I check next? Don't I have to have vacuum leak if it idles hot with adjusting screw in all the way?

Sticking throttle plate? I had one that was binding. Symptoms were sometimes, I'd have a high idle, sometimes I'd have a low idle. A tap on the throttle would sometimes cause a high idle to go back to normal. I swapped the throttle body, and the problem was gone.