Edelbrock Pro Flo 4 EFI

Has anyone had any backfire problems? Mine starts to backfire and hesitate when the throttle is over 20% open, and I cant step it WOT at all. Other than that, It works like a charm in idle and runs great with just a touch on the gas pedal.
Might be best to talk to Nate at the Edelbrock Forum
Pro-Flo 4 - Edelbrock Community Forum