Is my fuel pump on its way out?

I've got a regulated return system with the fuel pressure gauge mounted in the dash. The pressure is set at 66 #'s, and normally, under heavy acceleration, it drops to 60-62 #'s. Yesterday I noticed that it would quickly spike to around 74, then drop down into the low 50's. I tested it a little more by doing some longer than usual hard acceleration runs (floored from 0ish-85ish on freeway entrance ramps) & saw that the pressure would drop down into the low 20's.
It seems to me that with a healthy pump, a 4-5 psi drop would be normal, but a 40+ psi drop is a bad thing, right? I didn't notice any loss of power, & in normal driving, the pressure never really moved. Do I need to look into replacing the pump (it has 117k miles on it)? If so, is my best bet with an OE pump or is there a better (read: just as reliable but less money) aftermarket option? Would a lift pump like FASS or AirDog system fix the problem, or would that only be a 'band-aid' fix?