I know this gets asked all the time but I will rephrase a little bit. Chiltons says the fuel pressure should be set at 40-48 or something like that. First of all, are they talking about with the engine running? Second of all, with an engine basically maxed out with bolt on's, should the pressure be upped or lowered? Is it really that important to have it perfect? This should probably be sent to the FAQ board as well.

 

The injectors are designed to meet flow specifications at 43.5 PSIG. That is the theoretical ideal fuel pressure setting with no vacuum applied to the FPR.

That said, every engine is different. Some will run better with higher or lower pressures. Bolt-ons tpically do not change VE enough to require any FP changes. The MAF on your system should compensate with no pressure changes necessary. WOT tuning can be tweaked with altering FP, but the ideal method is to adjust power enrichment through injector timing if possible.