I ordered a db Dawg for my '04 and it arrived Thurs so I slapped it on and rode around my play track a little bit. First impressions were that it sure pulled hard off the bottom. Next- it's a lot quieter. My wife said so, too. Put the bike up and waited for today. Today, I went riding at the real track and gave it a good workout. I had a little trouble starting the bike but finally got 'er going. Wanted to foul out just a bit and it blew some smoke once started. Out on the track, I immediately noticed an increased low-end pull. Right off idle, it wants to bog a bit, but once you get past that, it pulls enough that I had to watch my throttle control on our dry track. After say 1/4 to 1/3 throttle, I can't say I noticed any difference in performance and if anything the db Dawg made the bike pull a little harder. We had a stock 450F and 250F and the db Dawg was definitely quieter- my wife said 20-30%. I'd forgotten the little sawed off wrench at home and couldn't do a back to back comparison, but I didn't feel any pressing need at all to remove the thing. By contrast, I put an FMF Q2 on last fall, rode it once, and immediately removed it. I lost low end power big time with that silencer. So, after 2 h, the db Dawg gets a thumbs-up from me.