Hi I have a 2004 Tahoe with a 5.3 flex fuel engine. It has a small cam, long tubes, and a cold air intake.

The issue that I’m having is that at idle my fuel pressure is only showing about 42-44psi with my regulator plugged in and only about 52psi with the regulator unplugged. I’ve already replaced the fuel pump with a stock unit and the fuel filter was replaced with a Wix at the same time as the pump. I’m getting rich fuel trims and setting lean codes for both banks. Does anyone have any ideas on what could be happening? Bad fuel pressure regulator?

 

Exhaust leaks or bad O2 sensors. A leak will fool the sensor into thinking it is lean, so the mix goes rich.

 

Ive smoked the exhaust to make sure that I don’t have any exhaust leaks both upstream O2s swap from .1v to .9v pretty consistently without any weird spots on a graph