Welcome to

!
Is there anything else done with the car - mods, replacement parts, etc? Have you tried pulling codes? Not that it might produce any with the car running, but it's not a bad idea to check anyway. How are you measuring fuel pressure?
Those questions out of the way, it could be a few different things. Bad hose somewhere, clogged fuel filter (I realize you said it's been replaced), weak pump, kink in a line, etc. Unfortunately, we probably won't be much help until we know more. And pics are always a good thing, both of the car (because everyone likes to see what we're dealing with

) and of whatever trouble area you may be dealing with (because everyone likes to see what we're dealing with).