The KDX 250 is jetted extremely rich stock. You will want to lean the main to a 155 or 158, put in a leaner needle (higher #), put in a smaller pilot jet (#38, I think) and if you really want the most out of it, you will want a slide with 1mm more cutaway (you can grind 1mm off your stock slike or purchase a new slide). One of the members in the KDX section (Duc748, I think) has assembled alot of useful information on setting up the KDX250, including many of the tips I used on my '91. Next time you do a top end, get a thinner head gasket from an '88 KX250 for more compression and better low end power.