Rich have a look at the card tuning article on the JustKDX web page paying particular attention to what circuit has the most effect at each throttle setting. Check each throttle setting independently, general plug readings aren't going to tell you a whole lot. You'll also want to insure you are using the proper heat range plug before you start the jetting process. Most KDX owners will find the BR7ES is their best choice depending on their riding style and conditions.
David