After 4K RPMs my Z feels a bit slower then before. I used to get about .940 volts on the O2 reading in WOT and lately its been down to .810-.910. I been told that I might need to upgrade the FPR because of the Walbro 255 80PSI fuel pump. What do you guys think?

 

How long has the fuel filter been in there? I've put 3 in mine. Car has 170,000 miles. Would go flat when I hammered on it. New filter fixed it.

 

Its a couple of months old. Sometimes when i'm letting the car idle it would backfire fire a couple of times.