I just woke up my stock 97KDX200 a little. First, I took off that K695 "slipper/slider" rear tire, and installed a 100/100-18 D773 rear "hooks up great" tire. Then, with the stock pipe still installed, I fitted a used stock KX250 silencer from a 2000 bike, went from 160/48 stock carb jet combo, to a 155/45. Then removed the airbox lid, and tyrapped that electronic box to the frame. To re-jet, you don't have to remove the carb, just unscrew the cap, and rotate it to gain access to jets. The silencer however required a small aluminum bracket be made to adapt the lower mount hole, but it breaths better, and sounds a little like a 250 with a deeper tone. The jetting and air box made a flat power turn into a crisp, "easy to wheelie" power. I also stiffened the front forks a bit by removing the rubber caps at the bottom, and running in the adjusters a few turns. The bike feels a little firmer now in soft dirt turns.
Total cost (I'm cheap) =
Tire - 68.00
Jets 12.95
Silencer from ebay auction - 18.00
Total =$100.00