food for thought, although you've basically proved it. You can use a mechanics stethoscope and put it on the injector(s). You'll hear the clicking of it opening. You can try it on your daily driver to confirm the sound.
Also food for thought, I had a bad tpi fuel pump that made the car incredibly hard to start if it sat for a week or more at a time. Static pressure checks were fine. It ran like a top otherwise though. Right up until I got into the middle of town one day and it packed it in lol
.. and confirmed, a TPI fuel pump will run a stock LT1. Likely the same pump.
..and if there is no vats unit in the car and you swear the vats has been deprogrammed then you should be good there.
.. I agree though, you should complete enough dash wiring to pull codes and see the check engine light. Esp. if you didn't do the wiring.
FYI there are a couple of power wires going to the PCM inside the 4 connectors. Funny things will happen if one of them isn't hooked up.
Also most of the car is ground triggered so grounds are very important. Motor to frame, battery to motor, etc etc.

 

what was the issue? Doing mine in a 86 gbody same thing happening to mine