After reading multiple threads and throwing parts at my 89 IROC 5.7, I found the problem. I replaced the distributor and the stalling at idle under load corrected and the rough idle is much smoother. I am including a picture of the pickup coil with multiple cracks in it, somehow I missed seeing this when replacing the cap, rotor and ICM. The parts I had replaced that helped but didn’t correct the issue was; IAC, TPS, coolant temp sensor, MAF, plugs and wires, oil pressure sensor, and ECM. Hopefully this information will help someone else with their idle issues.

 

Well sounds like it's all fresh now,too bad you threw parts at it not really needed but then again you shouldn't have any of those fail anytime soon.
Hey,where in SW WA are you? I live up near the town of Yacolt up northeast of Battle Ground.

 

I’m in Longview. I didn’t mind throwing parts at it, figured these parts may be harder to find over time.

 

Good possibility,glad it worked out for you neighbor.
I used to drive through Longview every day hauling wood chips from lumber mills to the paper mills,I drove for Walsh for four years.
The color of my Harley almost matched the truck. lol