I have to say Thunderheaders slip ons. I ditched my V&H true duals and went with V&H headers and Thunderheader slip ons and gained several horse and more torque. After hearing about the before and after dyno sheets at the shop I got my motor/cam etc work done at (Markum's in Pendleton, IN) I am a huge believer in Thunderheaders. The sound in 3rd gear was almost too much at first, but after the first couple hundred miles they got a little quieter....or I got deafer! LOL