NEW: rebuilt crate engine, Injectors, sparks plugs, 3x o2 sensors, plug wires, air filter, oil filter, MAF, IAC, DPFE, EGR,
also new front end + suspension, front drive line

truck runs great except for these 2 codes p0171 + p0174
_ smoke test >> no leaks
_ measured pressure at shreder valve : 54psi not sure about minimum??
_ Replace Intake manifold gasket >> same result
_ Replace MAF, IAC, DPFE, EGR >> same result

Been working on this last month with my mechanic, completely out of idea.

I searched forums to find the specs or minimum pressure needed at fuel line valve.
I hate to replace $$ fuel pump and fuel line damper.

Hoping that someone can give me minimum fuel pressure requirement?
Thank you,