It´s all or nothing with these exhaust changes. You will need to change your air cleaner and reprogram the ECM. Don´t change exhaust without remapping the ECM. These bikes run very lean and hot, it will only make things worse if you cheap out. I can tell you it makes a huge difference when you do all three. I like the Thunderheader...A lot of people don´t like to looks, but the sound and performance is quite unique to say the least. My 2 cents...