Fuel Pressure @ Injector Manifold - '89 2.9L Ranger

[cruby]

I have an '89 Ranger w/ 2.9 v6 w/ roughly 275K miles + 1 rebuild. Lately noticed loss of fuel pressure after sitting overnight. KOEO several times & can hear fuel pump run, then engine will start. I replaced fuel regulator & fuel filter & it now works OK. Truck still doesn't seems to run right, even before these changes. Hesitates & boggs down a bit on acceleration under load. I know it's old, but not dead yet. I got a fuel pressure gage & checked pressure while engine running & pressure at the injector manifold schrader valve is 29 psi w/ vacuum line attached. 35 psi w/o vacuum line. My Haynes says fuel pump pressure should be 30-40 psi, so it's a little below spec.

I've owned truck since new, and the fuel injectors & fuel pump have never been changed. I reused them on my rebuild.

So my questions are:
Is the 30-40 psi pressure spec for pressure measured at the fuel manifold, or is it at the pump exit?
Is the 29 psi indication that fuel pump needs replacing?
CRuby

 

[adsm08]

35-40 at the test port. Ford only issues pressure specs for the testing location, although pressure should be fairly constant throughout the system, until after the regulator.

Low pressure could be a clogged filter, a bad regulator, leak in the system, or a failing pump.

 

[cruby]

"Low pressure could be a clogged filter, a bad regulator, leak in the system, or a failing pump. "
Well, since filter is new, regulator is new, & no visible fuel leaks...then that leaves the fuel pump.
I've read up on pulling the bed to get to it. I see that I can get just the pump, or the pump + fuel level sensor. Getting the whole assembly since price is reasonable @ rock__.com & I figure after 25 years & 285K miles, the sensor's probably not far behind.
Got a new set of injectors on the way too.