Fuel pressure

Nope too old.. theres most like a vacuum regulator on the fuel rail

I have the same truck. You have a fuel pump that sends gas to the block because the mass airflow sensor is telling computer this and that for components of proper combustion on top of piston. So much air and so much vapor gets me proper ratio of 14:7:1. Rely on Delphi or Motorcraft fuel pump

You are aware that the relay sends power to the pump, not the computer. That black relay is in fuse panel near side fender or 2nd from near. Easy way to find out is start truck and pull out relay that stops motor.