Fuel pressure under load? help please

[Ozzy4194]

I'm chasing down P0131 and P0151 codes on my 97. I'm testing fuel pressure. New fuel pump. It seems good, KOEO 52psi , Idle 52psi , blip throttle it goes to 60psi, part throttle cruising 55psi, but at WOT it goes down to 40psi, then 38psi at 4500 rpm. Is that normal to drop like that at WOT? No fuel pressure bleed off when shut engine is shut off. It is a 5.7 auto.

 

[Scooterwrench]

Partially clogged fuel filter,cheap fuel filter that can't handle the flow or fuel pump on its way out.

 

[Ozzy4194]

It's a brand new Bosch pump and new filter. Had the same issue when the one year old fuel filter was in it as well. I'm trying to find info on what the pressure should be under load at WOT but can't find it anywhere. I also have the MPFI upgrade. Edit: I've ordered a new Delphi pump and Wix filter, I guess I'm dropping the tank again, sigh. Hope that does the job!