Alright, I am at my wits end here. I have a 98 K1500 Vortec 5.7 V8 TBI (pretty sure it's TBI)

Was sitting at a stop, went to accelerate and the truck just quit running with no warning.

Here's what I have done so far in troubleshooting:
I have fire, it will start with starting fluid and fuel poured into throttle body (I know, not a very smart thing to do)
Fuel pump is putting out great pressure (will edit and add pressure reading once test gauge gets here) But it sprayed the heck out of me when I lifted the metal supply line from the fuel distro block.
Fuel tank has 3/4 in it
Security PassKey is not active. It comes on during initial start attempt but goes out after a second or two, like it has always done.
All fuses are good in both engine compartment and cab.
Fuel filter replaced.
MAS replaced (it had a code during OBD-II test). Never heard the MAS causing a complete no start situation.
Bypassed the temp sensor at throttle body. It didn't help.

ECU? Injection spider? This problem has a very electrical feel to it, with the sudden shut down. How would I test those items quickly without 20 hours of teardown or some specialty tools? I have the manual, but it's not all that helpful with this.

This is my daily driver, and its crucial I have transpo, as I am a First Responder here.



Any help?????????

 

My 93 Sub with 350k on it is on it's 3rd ICM each time with symptoms you describe

 

Might be an ECM, as the previous post suggests, but before I condemned that, I would run around and check grounds, to be through. I am also wondering, is your ignition switch still working as it should? I don’t mean the locking part, be the electronics inside. Maybe something is not getting power? Or maybe did something in your fuel injection system get fryed, so it is no longer pulsing the injectors? I believe that 95 and later trucks have fuel injection, but before that it was TBI. Hopefully that gives you some ideas.