Backfire when hammering throttle

[Doowithblue]

Some owners are also experiencing higher than normal fuel pressure which can cause a specific tune to run richer than normal.

 

[Byam]

Fuel! Most of the tune are pretty conservative AFR. When its hot outside AFR are ways too rich,,,, i think its worst whit stock exhaust tune, to much fuel vapor......

 

[geez150]

To the OP didn't you just switch from stock muffler flash to performance muffler flash? If so,did it ever back with stock muffler? My sled with performance muffler flash would backfire here and there when I would let go of the throttle on a wide open pull. Very loud bang like a shot gun went off! But would not do it every time.