idk what you have done to your kfx already but if it's stock...
skid plates first (PRM or Pro Armor)
tires second (Razr2 or HD's)
nerf bars or a bumper third (PRM or Pro Armor)
that should be good enough to start racing bike is plenty fast stock to keep up with most your class...you can take the airbox lid off an spark arrestor out to open it up a little without having to buy a fuel controller..
plus it's your riding skills anyway that makes you win, but then again the kfx sounds pretty GAY compared to the other quads you're racing with with just a stock pipe
go to a hardware store and buy a tube of dielectric grease, take off your plastics an grease all your connectors, even the ones under the gas tank just skoot it out of the way.
Zip Tie your rollover sensor down too