Its basically unburnt fuel that goes throught the engine and hits either hot exhausts or other burnt fuel and fires up and makes this popping noise.
The best way to get ride of it is to get a PC111 and get your bike dyno'ed and that should sort it out.
The other way is to when your backing off the throttle back off it completely as when you hold the throttle open a wee bit more fuel is pushed in and just burns off automatically.
I dont mind it really and its not too bad as i run with the baffles in on my CCC cans.
