Fueling & Injection - Fuel pressure bleeding back?

2000 Z28, I can let my car sit for a few hours or overnight, come out hit the schrader valve on the rail and no fuel comes out. I have a new 255lph fuel pump, a new ls6 fuel rail & pressure regulator. Any ideas? I just bought this car and I'm getting so fed up of messing with it.

It will bleed off pressure over a few hours or over night per say there is. A certain pressure drop over a time that is normal.

But I'm talking about no fuel comes out. From what I understand its the fpr job to hold residual pressure in the rail. I've only got three guesses left : 1)Bad schrader valve ( which I have no idea how this would effect it). 2)Bad / wrong fuel filter (I read somewhere that the Corvette fuel filter had a check valve in it?). 3) Bad injector(s) which are leaking down while just sitting.

I thought the check valve was in the pump, but I'm not 100% sure

Does this cause a problem with starting or running the engine?
You can remove the rail with injectors, and pressurize the fuelrail. Place some cups under the injectors, and see if the injs are losing fuel.
What happens when you prime the pump? Does the car start right up?

The car seems to start fine. I was having a driving issue where the car would seem to lose all power, stumble but not die. Turn it off and back on and it would go again sometimes 5 miles and other times 50 miles. Since I've replaced the fpr its not did it so far. Idk, just thought it was weird not to hold residual pressure in the rail.