[NoDOHC]

Actually, I have know two people to install aftermarket FPRs on NA engines. Both of them removed the stock FPR and installed an aftermarket adjustable vacuum-biased FPR. They both set the fuel pressure (vacuum relative) to between 32 and 33 psi (stock is about 40) to improve power output from the engine.

This leans the engine up from the stock tune and allows it to make significantly better power. The stock tune runs filthy rich. Unfortunately, they both experienced strange symptoms on VDI actuation, 6PI activation and throttle transients (not terrible, but noticeable). I think it also would make the engine start hard, but I don't remember either of them mentioning this as a symptom.

Advancing the timing about 5 degrees from stock will also improve power output.

For reliability, either install an S5 primary rail or replace the Pulsation Dampener. I don't recommend removing it (although I did it myself with no ill effects).