Fuel pressure question

[95LZ1]

I have 1995 Z28 thats falling on its face only at wot. My fuel pressure is lower than I think it should be.. 28-32psi at idle 30-36 normal driving and 40 wot. It has a brand new Delphi fpr and new ac delco filter. Iirc wot should be 47psi. Is that missing 7psi enough for my car to stumble at wot?? The only ses code is for egr after the long tubes.

[95LZ1]

Just replaced fuel pump. It helped a little bit. I knew the pump was weak because pressure rapidly would fall to 0 after priming. But it's still not going past 40psi at wot

[Fastbird]

Spec is 43.5 PSI with vacuum reference off the regulator. Try sitting at idle and pulling the vac line off the FPR and see what the pressure goes to. If it goes to 43ish PSI, then I'd really suspect you've got an intake restriction and you're pulling vacuum at WOT. If it only goes to 40 PSI with the vac line off the FPR, then I'd probably think the FPR is funky.

[95LZ1]

Intake restriction??

[Fastbird]

Yeah, basically your motor is having to work to pull in air still. Really clogged air filter, junk in airbox, maf screen plugged up, something like that could cause you to not be able to see 0 MAP @ WOT.

[95LZ1]

I'll check tomorrow. I knew earlier today when I pulled the vacuum line off it went to 40 and that was it. Like it hit a wall

[Fastbird]

May be a crumby regulator.

[tleed]

Is this a stock engine?

[95LZ1]

The only mod is long tubes & 3" ORY