and to

Well since you've fitted a stage 2 filter, you might end up running the bike a bit leaner and ideally the Kev Mod is the best solution, they are only cheap and if I were you I would order one soon, simply send a pm to Kev and he will be happy to sell you one and post it to you but in the meantime, adjust the fuelling on your dash according to the link below, and keep checking your spark plug in the next few days to see if it is too dry and burnt or otherwise ok.

http://www.xt660.com/showthread.php?...=Co+adjustment