if u havent changed ur jetting since u got ur pipes, i would have to say that would be a great deal of ur problem.. its hard to give u an exact jetting size that u need, all bikes are different.. all i can say is that u should go to ur local dealer and get u several main jet sizes and prolly a 27.5 pilot and work from there, like locogato11283 said, the colder weather will change it up a bit too.. if u arent familiar with jetting then go to the jetting forum and im sure that a few people can help u out there... its not bad once u do it a few times..