Welcome to the world of xt660.com.

The bike came to you with the Kev Mods?..and you changed the settings?..what was it running like before you changed them. Mines set to 4 and runs sweet with no problems.For reference the mod has a wire coming into it which I refer to as 12.

Have you checked to O2?..settings at all as per the mods threads? https://www.xt660.com/showthread.php?t=630