Thanks all for the responses. Here I'll try and respond to all the comments, and recap a few things.

I've tested vacuum and it's normal.
I've checked IAC counts, and when hot and idling it's single digits, around 5.
It cannot be either cruise or throttle cable, because I was able to get the throttle to stick with both cables detached by manually adjusting the throttle.
I've remove the TPS and done the same, so the TPS is not adding any binding force.

It ONLY sticks when the engine is running.

Previously I thought I stripped two of the torx screws. It turns out I twisted and cracked the splines on my craftsman driver, so I ordered high quality Wiha driver from mcmastercarr, and it worked great to remove the screws.

When it's running, and the throttle is sticking, when I remove the map sensor vacuum line, allowing a direct port to atmosphere, the throttle returns to the close position immediately. The force from the vacuum / air flow past the blades is contributing to the sticking.

I am disappointed in two aspects of the throttle shaft. First, there is more play than I'd like, consider it has newly pressed in brass bushings (noticed in previous video).

Second, there is thrust play as well. It appears the shaft is centered by the blades, rather than by a thrust washer.
https://youtu.be/XNirKF3UBYk

The blades, are larger than the bore, or perhaps not round.
IMG_4983.jpg

The holes for the screws, also appear not centered with the holes on the shaft.
IMG_5001.jpgIMG_5001.jpg
IMG_5002.jpg

I'm curious if this is normal. These are custom blades for this bored out unit.

Right not, it appears at idle with the shaft on the stop screw, there was not much gap (0.03 mm plastic shim stock didn't fit). I'm not sure how the fuels getting around...it looks like there is a smaller gap in some areas, based on the wear marks on the bore.
IMG_4986.jpg
IMG_4984.jpg
IMG_4989.jpg
IMG_4993.jpg

I used some 600 grit sandpaper to remove all the sharp edges and nicks from the edges of the blades. I will work to recenter them as best I can and find a thrust washer to reduce the axial play in the shaft. I may try preloading the spring a full turn more, or adding a secondary return spring, if those other improvements don't solve it. One frustration I have is the significant deformation of the AL blades, from the screws, prevents them from properly floating while you tighten the screws. Are all the blades in the stock units AL? or are they steel?