[rdorman]

Generally that is caused by fuel coming out of the rear float bowl vents under hard deceleration. Cures include float bowl whistles, float bowl foam, or connect the two vent with a length of hose and open a hole in the top center. The last method is cheap and quick, if you don't like the look and it works, get some float bowl whistles and you will be set. I looked at the demon site and did not see where they come standard but I would be suprised if they don't.
Rick