You will just end up chasing your tail and spend tons of money to potentially solve nothing like that. There have been lots of good advise on how to simply troubleshoot your problem and you seem to completely ignore it and instead laser focus on something that everyone is telling you IS NOT the problem.
There is no fuel pressure sensor on your truck. The Fuel TANK pressure sensor is only used for EVAP system testing when the truck is first turned on and is not used in your application... regardless of whether there is a sensor installed in your fuel sending unit. The fuel pump itself is the same for almost all GM trucks/SUV's from ~96-2003.
Put a fuel pressure sensor on the rail and then test the pressure(I know you already did this). Record the pressure key on/ engine off. Turn key off and record how fast the pressure drops(PSI/second). Then do what spareparts said and pinch off the return line. Record the key on/ engine off pressure. Turn key off and record how fast the pressure drops(PSI/second). If your pressure with the return line pinched off is over 60psi and it doesn't bleed off very fast after you pinch the return line closed, your entire problem is the FPR. Full stop.