somehow my rpm is not reading correctly...my ecu is set to redlined at 8600krpm but when i punch on it, it stops at 7900-8000krpm.. so i hooked up a timming gun to the spark plug wire and revv up my motor while looking at the timming gun and my rpm...timming gun shows 4200-4300krpm while my rpm gauage shows only 3900-4000krpm.... any advice on what to do? need to fix this problem asap.... thax ht