I didnt lose any power when I put the Kazuma on...I gained. Also...dont take your cat off. I'm still running my stock cat. From what I've seen from experience, because I have had two seperate kazumas on it...one witht the stock resinator, and one without, I kept the one with the resinator...sounds a hell of a lot better. Here is what you do...get a high flow cat for a replace on your stock cat, get them to cut the kazuma and weld in your stock resinator, they'll need to cut it off your old stock exhaust. Then get the kazuma welded on, and it'll sound very, very sweet! =) Has a very original sound...like If I'm sitting in my house, and my wife is on her way home, I can hear her coming before she even gets down our road. lol Have fun with it...I still say Kazuma is the way to go for the 2000-2005s!