Bolt-On Kit 1 includes an air filter adaptor, UNI air filter and a straight header. With the increased flow from the air filter and header you will need a larger main jet. See the how-to section for information on drilling main jets. We also have main jets available in various sizes. Combining this bolt-on kit with the govenor removal will really wake up your GX340 or GX390. Picture may vary from actual kit.