If you have the old batery EFI, you can adjust the fuel delivery by very carefully adjusting the TPS sensor on the throttle bodies. You need to solder two test leads to the common and wiper wire and measure the voltage with the key on and engine not running at idle and WOT. Now adjust the TPS mounting to reduce the voltage at WOT by 0.010 volts (10 mV) and test the sled by reading the plugs and piston wash. If still rich reduce anothe 10 mV until you have it where you want it. It costs nothing and cleans the engine and gas milage up big time. Be careful, the adjustment is very sensitive and you can burn down just like a carburetor if you go too far.