suddenly running really lean

for some reason im not getting enough fuel pressure to rev the car as it should rev, yesterday my car ran good and today its running so lean to where itll barely run, im hoping its just a fuel filter possibly? do 240z fuel pumps just die out like this? i put the motor back together and cleaned up the fuel pump and it had a good vaccum, im gonna buy a new fuel filter tommorow but i just wanted to hear someone elses opinon, thanks.