Engine wise I started out with weld in mufflers, I wish I would have used that flow for cat-back with bigger pipes, any how then I got a K&N, Steeda Pulleys, My Shaker that might not do anything hp wise (CDC claims 2% or maybe its 2hp?), I just put on a 75mm Accufab combo (havent dyno'd it with that yet) any how thats all pretty basic stuff for the HP I've gained I'm quite happy.