JTS01Z28

Wondering if anyone can help. My buddy's '02 Tahoe flex fuel 5.3 gave him problems yesterday morning. He said he had to hold the gas pedal down some to keep it from dying at idle and at lower speeds. I did some checking over of it and it had no DTC's or other obvious problems. I did do a fuel pressure check and got 42 psi at idle, 52 psi with the vacuum line off the regulator. Engine off with the pump priming I got 52 psi then it drops down to 46 psi almost immediately after the pump stops priming, then it bleeds off another 10 psi in 10 minutes in pressure leaving the key ON & the engine OFF. Pulled the vacuum line & saw no fuel come out of the fuel pressure regulator while the system was pressurized. So, is this ok? If not can you get me some specs for this truck's fuel system? TIA.