Just got an exhuast power tip for the 400, and it really opened it up. I used to think it wasn't very fast at all, but now this thing's got snort! You can get them on ebay for almost any quad and they include the bolts and a spark arrestor screen. If you're looking for noticablly more power and give your quad a mean exhuast note, you should check these out. Worth every bit of 30 bucks.