Yes, 65psi is spec for returnless fuel system.
Higher RPM loss of power can be collapsed Cat or Muffler, limiting exhaust flow at higher RPMs but that should show up as vacuum level dropping as RPMs are kept at 2,500(for example)
As exhaust system builds internal pressure, less and less air/fuel can be pulled in so power drops and so does vacuum.
This is about the only thing that will reduce engine power and won't cause computer to set a code
I would expect Lean codes if fuel pressure was the issue, especially if you feel a lack of power.
With lower pressure or flow(fuel filter) the computer would have to keep fuel injectors open longer to compensate, and that should set a Lean code for both banks.
So if possible check for codes.
Other thing would be to clean the MAF sensor, it could be under reporting air flow at higher RPMs so computer is not adding enough fuel, but again i would think there would be a code for this, unless MAF or air cleaner has restricted air flow at higher RPMs.
Check air tubes from rad support to air filter housing to Intake manifold, may be a critter has decided to move in, lol, and there is no "code" for critter intrusion, so I guess this wouldn't set a code either
Long shot would be TPS(throttle position sensor) it could be telling computer you are never pushing gas pedal down more than 1/2 way.
Try this test
Press gas pedal down all the way and hold it down
Turn on key and try to start engine, holding gas pedal down all the way!
Engine should
not start, it should
not fire at all
Fuel injectors will be shut off; gas pedal to floor with engine off will cause computer to set "Clear flooded engine mode", spark stays on but injectors are off, as soon as you release gas pedal injectors will start up again.
If no start happens then TPS is OK
If engine starts then TPS is not sending computer correct voltage for WOT(wide open throttle), so worth testing it's operation more closely.
Another long shot test is for the EGR system if you have one.
Remove EGR valves vacuum line, and plug the vacuum hose, this prevents EGR valve from opening.
Drive truck and see if you get better power.
EGR system is well monitored but.............stuff happens
IF EGR valve is opening too much it will lower the power a lot, it should set a few codes if that was happening but the DPFE sensor(that monitors EGR system) is a known failure point in this system.
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