Well,my modification is intake,header,exhaust,MSD SCI ignition,Crane cams PS91 coil,SARD fuel pressure regulator,spoon sparkplug cabel, and denso iridium IK20 sparkplug.Before I change the fuel press regulator this already happen, even I use a standard sparkplug. So do you think this is normal? I mean the car is running fine no cel's at all. How many PSI I should set my fuel press considering my modification then? thanks.