i just put a k&n on my raptor and took the lid off. i used the gytr jet kit and there recomened jeting (L-155, R160, P 25) it idals fine and if you give it gas it goes no problem, but at a stedy speed it sputters and when you give it gas it hesatates then moves out fine i cheacked the plug and it looks ok to me any help would be great thanx.

 

Sounds like its lean . Try pulling on the choke while its doing the sputtering, if it gets better, then youre lean. If it gets worse, then its rich. Heres an article on jetting that will help.
jetting