Hello All
Looking to get some help from others on my consistent issue.

06 Silverado WT 4.3
Bought this with a Crank No Start but all subsequent cranks starts up just fine and runs great. The previous owner told me about this issue. He had a new Delphi Fuel Pump put in but issue continued.

We bought it and not knowing how old the pump was we replaced it with a new Delphi pump with new O-ring and new locking ring. Issue continued.

Next we put in a fuel check valve near the tank.
issue continued

Next we replaced with 8 new GM injectors.
issue continued.

We hooked up a pressure kit to the Schrader valve. Accessory on pressure is 50 and above and while running no pressure issues at all.

Next we turned it off and we can see that pressure is being lost right away and them move to accessory and pressure resumes.

We have seen some say that GM OEM or ACDelco pump would fix this but is over $500 for one.

we are at a loss what are we missing ?

any help would be appreciated

Thank you