sultan(ZR-1)KSA

hi guys its been a long while since i posted any problems but it seems to have arrived and in Ase's

OK here goes

on idle every thing is fine going up and dawn the RPM on light throttle and all is good
nut once i get on it hard and go above 5000RPM i start to lose pressure
i did some testing to see what is damaged

1-i closed the feed line to the regulator and the fuel pressure went way pass 100PSI , so the fuel pumps are good

2-i burrowed a fuel pressure regulator from a Friend and it showed the exact same symptoms

i guess the only other thing is the fuel filter to change and that is what i will do tomorrow

what do you think guys