Backfire on deceleration?

I have the same problem with my 5.9 factory EFI Magnum. Someone told me it could be the fuel sync, but I can't see how the injectors spraying the intake valve a little too early or too late could cause an issue on the exhaust side.

@vegasanthony have you checked your fuel sync setting? I'm running OBD1 so it's not a simple thing for me. I used my best guess and seat of the pants to tune the sync.