Yearly ish update.
Fixed the reduced engine power issue but cleaning up all my grounds everywhere. Not surprisingly, my voltage improved as well.
Then the truck started surging while driving, and it would shut off and just crank without restarting. So we pulled the bed and replaced the fuel pump, thinking that would solve it. But of course it didn't, it still does the same exact thing.
So I've gone through and tested a lot of the electrical components just to rule them out. The injectors ohm out fine, with and without adapters, they're getting the proper voltage with and without adapters, the ECT sensor ohms out fine cold and hot, the maf is working properly, TB, TPS, xlink all check out. Changed the oil pressure sensor since that was being funky for a while, but that didn't make a difference which is what I expected anyway. The fuel pump is pumping fuel to the rail, at least initially. I don't have a test port but I need to figure out how to get a gauge hooked up and see if fuel pressure drops off at any point when it gets warm.
It'll run til operating temp or close to it, then shut off, then just cranks and cranks. If I let it cool, it will start again and run til it gets warm again.
Not passlock or vats related, not tune related either. I sent logs to Richard (Atomic) and he said air and spark look fine, so probably something fuel related.
Mike, Cleanoh4, is convinced it's electrical, which I think it probably is too. Something that gets hot and causes issues then cools and works. So I'm basically to the point of just going through circuits and checking everything which kinda sucks.
Oh, and put these on along with a new bumper when we had the bed off.