SO did you ever figure anything out about this issue?

 

Sorry to leave you hanging. The short answer is no. This has been partially due to bad weather on the weekends (why does it have to rain/snow/flood on my 3 days off each week?), And partially because I've been lazy.

I did pull the IAC hoping to spot something, but there were no apparent drag marks and everything is still shiney clean in there.
I had an OH SHHHI... moment a couple days after posting this that might offer some insight to someone. Someone pulled onto the highway In front of me while running about 70 mph (2300 rpms in 5th) and my trucking instincts kicked in. While on the brakes hard I jumped from 5th to 3rd for the compression braking. Rpms jumped to about 3800, not sure of ground speed at that point... I'll have to check that (pardon the large attention sp- oh look, shiney. Lol)
Once my nerves settled down I realized that the idle was behaving like it should. Smooth drop to 750 from anywhere in the rpm range, with any throttle position. This lasted for about an hour. Unfortunately I haven't been able to duplicate the results, so it might have just been a fluke. Only thing I can figure is the sudden high vacuum caused something to seat temporarily, but I'm still not sure what or where.

 

check the butterfly shaft for wear by trying to wiggle it . start the engine and open the throttle then close it then try to force it closed even more by hand . it might also be a slight air leak . might also be the throttle position sensor.

 

Didn't think of the shaft being worn because of being a fresh bored out one from HiPoTec, but it is possible.
The butterflies are closing like they should still.
I'm still leaning towards a vacuum leak, I just can't find it.
If you read the first post, I've tried and tested 3 TPS's, all with the same result.

Good ideas none the less. Thank you.

 

Back after this finally.
Watching the scanner when the throttle hangs, TPS is .76, throttle position is 0%, IAC count jumps to 60 (target and actual) when throttle closes then steps down to 20.

The couple times the throttle didn't hang the only change was IAC counts when the throttle closes. It only went to about 35, then steps down to 20.

This has me leaning towards a glitch in the pcm now, but I figured I would see what folks in here have to say.

 

What is engine load doing while that is happening?

 

5-7%, same as idle.

 

well that's just weird. And the PCM actually WANTS IAC there? What does it say about Target Idle?

 

Target idle showed 752.

 

Was that where it was at?

I wonder if the PCM is a tad confused.....