Did my FPR go bad??

Hey guys, long time no see!

I wish this were under better circumstances, but I could use another set of brains on my car.

I've been having issues with my '76. She's been running lean and cutting out under load. (I know she's running lean because I checked the plugs -- all white).

3 years ago I replaced the fuel filter, FPR, and the injectors.

First instinct was that, somehow, the filter had again gone bad (it HAS been about 15 or 20k miles). I replaced that, and the car was working pretty well for about an hour ... then again the misfire came back.

I went and bought a fuel injection pump tester and hooked it up to the cold start valve... and here are the results...

When switching the key to "ON" the gauge shoots up to 37 PSI right away.

When starting the car, and letting it run out to idle (mine is set around 850ish RPM ... though right now it's sputtering a bit), the gauge reads about 29 psi.

If I rev, the pressure spikes back up to 37 for a split second, then drops back down.

If I try to hold a higher engine speed (i.e. 1500 RPM), the pressure fluctuates around 30 psi.

So, is it pretty likely that my 'new' FPR has gone bad? ... Or is it likely that we're looking at something more dire (i.e. blockage in the tank?)

Thanks guys!! (and gals)