issues after nismo fpr install

[aurora61]

I have a stock sohc with a walbro cause the original fuel pump died on me. I was running rich because of it, and i decided to buy a nismo fpr.

After the install, i immediately noticed a different exhaust note. The best way to describe it is that it sounded like a subaru impreza's boxer engine due to its rumble. Normally, the exhaust sounds smoother. I drove it around and it seemed to run fine despite the new sound...but then again, i babied it cause i was afraid of causing problems.

After a few minutes of it, the engine/exhaust suddenly returned back to its usual sound...aka everything was fine. But after a good while, the weird rumbling returned, but was gone after 1-2min.

I have my fuel pressure at 34-36ish psi at idle, and 42psi without vacuum...i read somewhere that this is wat it should be, but i could be wrong

Can someone diagnose my problem?

[GTR PrYdE]

did you fix this?

sounds like an injector was going out.. you can unplug each injector and see if idle changes