I am having a problem with low fuel pressure. It's not like my pressure is way too low.. the car drives but not enough fuel is being delivered for full boost/WOT. The car will misfire and stutter.

Pressure at idle should be 38psi but i'm getting from 35 all the way down to 30psi sometimes.

the fuel pressure regulator appears to work as it should. When i remove the vacuum hose the pressure goes up as it should, and there is no fuel evident so the diaphragm inside seems to be functioning. It holds pressure as it should when the car is turned off.

I have checked all the fuel lines and replaced some. I have seafoamed the tank and that doesn't seem to fix the problem. i have inspected the sending unit and put in a new gasket, and there do not seem to be any particles in the tank clogging anything up.

The fuel filter is not clogged.

The fuel pump is a pretty new MSD 255lph external pump so I can't think of anything else besides just replacing the pump yet again.. any thoughts. It is getting 11.7v at idle and I know that's not 12v but it seems to be within tolerance for not causing an issue..

 

Ever think of putting a dent in the fuel pressure regulator? That should raise the fuel pressure.

 

Misfires under load would point to a failing coil pack(s) / weak ignition (sparK).

 

new packs all that is verified good...

it's just not getting enough fuel... an EFI car getting 8psi below what it should through the rev range is starved for fuel