Gary

Because either system has a wide band O2 sensor, they are programmed to start just slightly rich like any EFI system and then run at 14 to 14.5 A/F ratio. You can change those A/F ratios to anything you want.

To me, The safest way to start a new motor in with one of these EFI systems. They will only be as rich or lean as you want and if you don't change them, they are programmed to supply fuel and spark at optimum levels.

If I were you, I'd call Holley or FAST and talk to them. The Holley Techs have been great with me.

Bob