My 1990 KDX200 was running fine in all ranges until I replaced the MX style silencer with the original spark arrester muffler. Now there seems to be a flat spot at high rpm but is seems fine at low throttle settings. It has a fatty pipe, rad valve, 48 pilot, 1173 needle and 155 main jet. Compression is good and the power valve appears to be working. Is anyone running a setup like this, and if so, do you have any suggestions for me?