Turned out it was the square connector on the inner fender well from the engine harness. The pins inside were corroded and funky looking.
Well, I did some checking. The wiring harness must be different in a '95 vs a '99, because I do not have a connector as you describe.
some info: I have an identical truck; I have swapped the PCM and the IDM out, made no difference. painstakingly checked all the connectors, including UVCH.
I did finally get to check the fuel pressure. When I turned the key on, it was moving from around 25 - 50 psi, going up and down some. (running, it was around 50 psi, varying about 5 psi either way) I took the regulator/relief (FPR) apart on the top of the fuel bowl, and I found the small rubber washer on the "plunger" had swelled, and was very loose on the plunger. I swapped it out with my other truck, it is now back up to a steady 70 psi, seems like it has helped.
I am still getting an lightly erratic idle though, and can still feel some pulsing going down the road at times. It seems most pronounced after the truck has been driven and allowed to sit a little while, not totally cool off.
I have an original black (new) CPS in this truck. Buzz tests, cylinder contribution tests, all show up ok. I physically checked the clearance on all eight injectors, they were all almost identical, around .003-.0035 clearance.
(early '99 f350)