I just installed Vance and Hines pipes with the Power Commander V and had my bike Dyno Tuned each cylinder maped the bike runs great, starts easy, sounds awesome, but when down shifting or just let off the throttle it makes a crackeling noise and sometimes a slight backfire that is really annoying me,
The dealer said that's normal with aftermarket pipes it that true?
I have the 09 Kawasaki Vulcan VN 900

 

I too have heard that popping can and will be an issue on how you tuned the pc. Also was told that you can also tune most of the popping out when tuning the pc. I do not have the VN but my tuned ZX seldom backfires. I would chat with your tuner some more and see what can be done. Maybe blip the throttle when down shifting to ease up on the backfires?