need more power

air filter exhaust and reeds will prolly be the most common answers i would think. depends on what you want to spend and what you want
 
lose about 40 pounds ..its free!

remove the airbox lid get a KN filter and rejet
 
^^ what flotek said about intake. and if you dont have a aftermarket pipe, not cheapest solution but you would be satisfied.

maybe a gearing change to your riding conditions. wat type of stuff do u ride?
 
i got a couple miles of trails behind mi yard. mostly trails but thes a track we build with a lot od dirt jumps nd tabletops nd stuff.. but there is alot of water too we cross through
 
well this is what i started with, vitos high flow intake(for sale), airbox lid removal, reed spacer, and vitos carbon flex reeds on stock cage, got a bunch more now. but you will see a difference and th stuff i listed will cost you less than a hundo shipped off ebay or buy em on here, also buy a 14 tooth sprocket, 15 bucks shipped.
 
the pipe is where you wanna start. this is what you build everything else on.
the pipe will dictate your engine's max rev, the peak horsepower, how far the engine holds peak horse, the nature of the power curve, the bottom end come on, the over rev.....
start w/ the right pipe. do your research, and make sure you get the best pipe for you particular application.
then from there you can have the jug modded by a knowledgeable builder (i ALWAYS recommend kennedy_power) who will tailor your exhaust port to match your needs, match the head design to compensate for the loss on exhaust port design, then the transfer ports.....etc etc...