what can cause this? it kinda makes sense that i use more gas after replacing the fuel filter cause there is less fuel flow ristriction but i think i was getting 360miles/tank and now i might be just at 300 or lower.

Why did i change it again?

What else should i check for poor gas mileage?

That doesn't make sense, you should be getting better mileage, and better performance!

I know but I cant tell that much of a difference...i changed it a few days ago so i'll have to keep an eye on it for a few weeks and see how my mileage turn up in the next few weeks and performance wise...i'll find out after saturday when i get my GR-2's installed

Is the fuel filter you used as a replacement a Nissan part, or some other manufacturer?

original Nissan part.

Try reseting the ecu.