what to rejet!?

[Lil90man!!]

Ok i have a basic understanding of rejetting but all i'm gonna do is put a new hmf exhaust on my 300ex, i don't wanna get a new airfilter or take of the airbox lid either due to ALOT of mud/water around here so what do u guys think about, right now it has a 122 main and the pilot screw/jet and needle are stock(dunno what there set at don't really wanna tear into carb unless really nessaciary(sp??) but i wanna make sure my bike is running good and i'm not runnin lean n gonna screw it up so will with jus a slip on will it need to be rejetted and if so will i just be able to increase the main or will i have to take it apart and mess with the needle and pilot jet?? any help is greatly appreciated:cool:

[stocktires]

if you want a good filter call sparks up, they sell a k&n with a foam wrap which gives you the best of both worlds (very clean air, and higher flow!).
The only think you probably have to do with a completely stock motor with a slip on, would be up the main probably only one size. So get a 125 main and if it runs good after that, id say leave it alone.