Just picked up a 05 1600 Nomad with 4000 miles on it. The previous owner says it has a power commander installed. I'm not sure what that is. From time to time when decelerating it back fires. Usually slight but once at about 70mph when I let off it gave me a loud one. Like a shot gun. It has Vance and Hines exhaust. Should I be concerned about this and is there anything I can do to remedy it?