I have a 1995 VR-4 Spyder that I'm experincing bad hesitation (believe to be misfiring) It was slightly present when the car was stock. Now that I have added Stillen Intake, Borla Exhaust, HKS EVC IV, HKS SS Blow Off Valve, Aluminum Flywheel, Underdrive Pully and HKS Timer, it has made the problem much worse. I'm in Colorado where mostly 91 octane is sold but we have less air. Also I have a friend with the same modifications as me using 91 octane with no problems. I have replaced the plugs and wires and ingition coils and neither has helped. My last guess is the computer but I don't want to spend the $ if that isn't it. Any help will be greatly apreciated.