I gathered some data.
First of all, when i cranked it up for the first time today it started right up, no issue, so apparently its going to be intermittent.

Went to my friends house (used to be mechanic at Cadillac dealership), borrowed his vacuum gauge and fuel gauge.

First checked fuel, with key on pressure rises to 58 psi but as soon as you turn the truck off pressure immediately starts to drop, first to lower 50's then it will drop to 20's 30's within the next 2-3 minutes or so.

Checked the vacuum line for FPR, it was pulling 18 mm-Hg, so its within spec, then while running and the vac line pulled from the FPR, the Fuel pressure was about 60, as soon as you apply the vac line to the regulator the pressure dropped to about 50 psi.

So using my Chilton manual as a guide to do these test, everything looked good. The only thing that did not hold up was the pressure after turning the key off. The book says that for at least 5 minutes after turning the key off i should maintain pressure within about 5 psi i believe, my results showed a huge decline in pressure.

Pump diaphragm not holding pressure maybe?

 

Most generally they will start fine when they sit overnight, make a short trip in a store for 15-30 minutes and then she cranks forever! Cause=fpr I'm almost certain this I stout problem, I'm not an Internet warrior, I run a shop and work on mainly LS engines

 

Pinch off the return line and test the fuel pressure again. If it still bleeds down, then pull the fuel injectors out of the intake manifold(leave them connected and retained to the rails). Key it up again, and look to see if you have any injectors leaking fuel.

With everything you have described in all of your posts here, it's either the pump, a leaking injector, or a bad regulator. You also have a fuel sender problem. I'll guess that it's your pump, but do these checks first.

If you end up replacing the pump, and need the whole module, I'd recommend a Denso module. They are being sold by Napa, Carquest, and several other parts stores, and it's the EXACT same part you would buy from the dealer. But for a better price.

 

So what was it?

 

Since the issue i just leave the key turned on for about 2-3 seconds before trying to crank and i have not had this issue since, although it is a bad method and just avoiding the issue. I have had the truck tuned since then and the tuner didn't mention anything about the truck running lean at WOT, regardless i need to change the pump before i'm left on the side of the road. I didn't re-read the comments but i think i posted that both pressure and vacuum were okay for the most part.