Running rich: Walbro 255 with stock FPR

[Project240]

I've only had this car for a couple of weeks; I haven't checked yet, but I'm fairly certain it has a 255lph pump because it seems to be running pretty rich. I can smell fuel with the car running, and it bogs quite a bit in the middle RPM range. At around 3K I can hear it spool, but it feels like something's holding the car back and then it backfires when I shift.

Would it be safe to assume that the fuel pressure is too high because of the upgraded pump, and go ahead and order a Nismo FPR? I'll be checking the other obvious things as well, like boost leak/spark plugs and gapping, but I want to get this solved as soon as possible, so if I need a new FPR I want to order it soon. Like today

Bueller?

[Hijacker]

A larger capacity fuel pump will not increase fuel pressure. I run a 255 with a stock FPR and my idle pressure is 43 psi.

Try changing your O2 sensor to a new unit if you haven't already. Also, check your injectors to make sure one isn't leaking. I've had leaky injectors dump extra gas and bog a car down before, and also stumble the idle after the car has warmed up.

Lastly, consider replacing the temp sending sensor.

If you still think it's your pressure, hook a fuel pressure gauge up first and confirm it's too high.

[mi240sx]

I'm having the same problem, another thought is the pump does have a bypass on it so if your fuel pressure is to high it will bypass it to keep from damaging the pump. I'm going to try some things(one thing at a time trying not to change to variablies at once) that the guys are saying and see what I have the best results with starting with the 02.