Issue:
Started and ran fine, then started sputtering, loss of power, backfiring, then died and wouldn't restart, 20 minutes of driving after about 1 year of storage.
This won't help anything, but the only code that showed up after the short 20 minute drive was P0161.

Vehicle:
1999 Chevy K1500 Ext. cab Short Bed, Automatic, 5.7, 69,000 miles (private party)

Truck has been stored for around 1 year, 1/3 tank of gas with sta-bil additive and battery maintainer.

Description:
Now its time for emissions, uncovered it, after 2 cranks it started right up and ran fine (AC still blowing cold too). Drove it about 15 minutes, ran it through a soft touch car wash (no water getting to the top of the engine). After leaving the car wash, it started to sputter and hesitate, yet still drivable, back to the house. After sitting in the driveway (this lasted for approx 10-15 minutes MAX), when revving it up, it hesitated . . . sputtered . . . backfired and when I let off, it idled okay. I was able to REV it up by jockeying the accelerator and it seemed to be okay once it got to the higher rpms, then when it came back down to an idle, it idled okay, then I repeated the process jockeying the accelerator, sputtering, etc, . . UNTIL it just died on its own and wouldn't start back up at all. It just cranked over after that. I replaced the ignition module (as it sounded like the culprit) and nothing. THEN, I checked for spark at the coil, and there IS spark. I checked for fuel pressure at the fuel rail. When I turn the key on, you can hear the fuel pump whizzing (as normal) and the pressure eases its way up to around 40-45 or so (looking at the angled gauge through the windshield as I turned the key on), then the pressure eases back down to zero psi after the initial prime/pump shuts off. When I turned the key back off,the pump came back on and the pressure works its way back up to around 40-45 or so before the pump shuts off and stopped whizzing (as it normally sounds), and it eases back down to zero psi. I'm not sure where the pressure is going.

I can't seem to find ANY info online that matches the issue that I have. Is it a plugged fuel filter causing it to backfeed to the tank, if that is even possible (will probably change it anyhow)? Is it the fuel pump, its whizzing like normal when turning the key on and off and builds up pressure (of course, then it drops off again when the pump shuts off)? It it a check valve/ball on the fuel pump? Some say its a stuck injector, some say a leaking or stuck fuel regulator.

If the fuel pump pressurizes the fuel rail, then why wouldn't it start. . . the pressure was there, RIGHT? There isn't even a hint that its trying to start. Could it be in the electronics? Please help, if your not too busy. Thank you