jetting a bike is just making sure its running the correct air to fuel ratio do a search on and you will find all kinds of answers. as for mods that bike rips i would spend my money on first of all keeping the bike fresh (tires,top end,maintenance)and then if i had extra money i would get a skid plate,good chain,a good set of bars that won't bend in the first tip over like the stock ones and if you really want to spend money have the suspension set up just for you (riding ability and weight)not untill all that if there is still money left then i would worrie about doing engine mods even then i would not do a pipe untill i smashed the stock one i would first do internal mods like a reed cadge or adding a tooth to the rear sproket or even porting why spend $200 on a pipe when if you fall over (and you will) you can smash it when you could buy a reed cadge or porting or gearing that won't get wrecked in a crash.