Fuel pressure question
 

So we've been trying to track down an issue we've been having with the boat, runs great for 15-20 minutes then starts to miss and gets progressively worse as you keep driving. Boat has a holley blue fuel pump on it, we put a pressure gauge on last night and it had 7.5psi of fuel pressure then after running on the hose for 20-25min in was down to 6psi but never missed or acted funny. Put a new fuel pump on (the original was 25years old) and it runs 3.5psi. My question is what fuel pressure should I have? should i adjust the regulator to run 7.5psi? Or any other ideas why it runs awesome for 20 minutes then starts cutting out?
Motor is a 525hp 496ci, full roller, bary grant 950cfm carb. we've replaced the fuel filter, all fuel lines, coil, cap, rotor, pickup, plugs, wires...
I'm leaving for the shootout today after work and if the new fuel pump doesn't fix the problem i'm all out of ideas.
any help is greatly appreciated! Thanks!

Chances are, The wiring sucks or the fuel pump sucks.

Always make sure antisiphon valve isn't sticking or just get rid of it all together.

6-8psi is fine.

Read these reviews:
https://www.amazon.com/Holley-12-802...t&pageNumber=2

Oh, you didn't happen to mount the new pump higher and/or further away than the old pump did you ?

Pump is in the same spot as the old one was.
How do you check that the antisiphon valve is working correctly?

Have you verified fuel vent? Good Luck!!!

Yes it is clear. I was hoping that was it and it would be an easy fix.