1995 Chevy K1500 bad hesitation when warm only

I’m in the middle of trying to track down and fix this issue, but recommendations welcome.
95 chevy 350 auto K&N stock type air filter, cheapie stainless exhaust that wasn’t complete so part leaks after cat/muffler joint, otherwise stock.
This only happens after about 20 miles of 70mph driving or longer of course.
It mostly happens when taking off from stopped, but also at slow speeds if the pedal is in the right position, and rarely at cruising speeds.
It just wants to stall unless I press the go pedal farther than this sweet spot, which is usually too much and unsafe.
I’ve noticed some weird surging or lack of power at speed, but I recently also found #3 plug wire was not on the plug all the way and fell off when I went to pull it to start a power balance test. Didn’t do the test as I was hoping this was my whole issue, it wasn’t, it was still warm and it tried to stall just getting out of the driveway. So I may need to watch for this symptom later, I may have helped that one at least.
This really all started about the time I rebuilt the TBI. If I remember right I was having hard start or no start issues before this. So I bought a rebuilt one off ebay, but it ended up not being the right one and I had to use my original lower half, I did clean it up real good though. Put on the other top half as new injectors was one of the main goals. Also put the new IACV on the original lower body.
The TPS is only 2 years old, but I have not checked it’s voltage yet. It was the main reason to reuse the original lower body, the tps mount was not the same on the rebuilt unit. I do have ground and 5 volts at the plug and 6kOhms that slowly descends to about 2kOhms when operating the throttle. So it seems it should be ok…
Plugs wires cap rotor also done 2 years and 2K miles ago, it doesn’t get driven much since it gets less than 15 mpg, but should be ok still.
I did check the EGR though as it is one of the top ‘guesses’ for this issue, all seems fine though. Pulled it, pushed it in which took some force as the nipple has a much smaller hole than the nipple would suggest, put finger on nipple and it did not move, hole to intake is wide open from what I could see.
I ran it with the egr solenoid unplugged and it threw a SES light but still did the stalling bit, so solenoid also seems ok. I though maybe internal seals were creating a vac leak when energized, it has another nipple not hooked to anything, prolly to let in atmosphere to the egr actuator. I wonder if a hand vac pump can be hooked up here to quickly test the egr actuation?
Sprayed carb cleaner all over anywhere I though vac could leak, no rpm change.
No ticks or obvious sparks on the plug wires either, checked at temp at night but not with water…
One of my worries is the fuel pressure regulator wasn’t put together correctly or just isn’t the right spring or isn’t adjusted right. So I want to check fuel pressure some time, but a little unsure how. I’ve read I need to tee in to the inlet and check there, but is there a kit I can rent?
I’ve also been researching the hell out of this issue and there are TONS off ppl writing about the same issue, but almost no fixes. gmfullsize.com forum was almost no help at all, I though for sure there would be a lot of useful info there, but it was all guesses and no real answers.
Oh and I also read it might be trans related and I looked and it was overfull so I sucked all I could out the fill tube and put some fresh back in. It does read low/cold when running, but when warm it’s the same level and I do see bubbles. But I kinda debunked this theory today as it tried to stall in park pushing throttle to the just past no throttle into the spot it usually acts up.