I had these installed on friday. My current mods are nismo exhaust, Mrev+w/spacer and UR Pulley. The first thing i noticed was much better throttle response. Maybe this sounds wierd but i feel a difference like when i first installed the UR pulley. The butt dyno does feel difference, while i dont feel a pushed back in the seat difference, for sum reason i feel the car pick up speed a lot faster, maybe its the smoother throttle response? The exhaust note is even nicer now than before... well thats my impressions Headers go on Monday