Earlier this year I noticed that as my car ran longer, the fuel pressure would drop off from ~62 at idle to ~55 at idle after about an hour or so. At first I thought it might be the gauge, but I also noticed that my WOT air fuel ratio goes from a near perfect 13.0:1 around 10 minutes after starting, to ~13.5:1 after an hour of running. So maybe the fuel pressure really is dropping off. I really don't believe that it's the Racetronix PnP setup. So maybe the factory fuel pressure regulator is acting up. Can I put a high quality regulator between the fuel tee in the main line and the factory regulator to solve this problem? I REALLY don't want to drop this fuel tank agian...

 

Series regulators will make series drops, or a high
head pressure. Probably **** off the fuel pump as
well as elevating the rail pressure hugely.

Wonder whether this might relate to the fuel tank
being drawn down, I think the regulator has the
tank internal pressure as a reference and the tank
is pretty much sealed except for EVAP stuff. So
if the tank is drawn to soft vacuum the regulated
line might follow?