are you sure you even have a problem man? My bikes always crackled and popped a bit when closing the throttle from high revs, and theres certainly nothing seriously wrong with the engine (its done 20,000km without a hitch since i got it) - in fact i kind of like the extra sound effects...!
Thing is why im worrying is that it never did it before.. and it just started doing it recently... but maybe its nothing.. maybe it is something