Mine was noticeably slower to gain RPM after about 5K. I never dynoed it, but I would estimate 20-30 hp off the top. Good kick off the line, I would say the boost threshold was around 300 rpm lower. It seemed ready to rock at any time with good torque, it followed your foot well. I wouldn't recommend it unless that is what you are looking for. I would say there was less benefit from the breather mods with those housings. For me, the loss up top wasn't worth the torque.