well if you get a JDM header you are going to have to also buy a cat. I got my JDM DC stainless steel for $399 shipped and paid $212 for my SMSP cat and JDM donut. I really like the set up, but the butt dyno didnt 'feel' a big improvement. Im running rich as hell though so with some massive fuel tuning i think ill see a major improvement. My verdict 2.5" collector >>> 2.25" collector. What kind of exhaust are you running?