Last time I told you I'd used Yamaha's GYTR Power Tuner to take the edge off the YZ450F's low-end hit. Since then, a conversation with Doug Dubach convinced me to try one of his company's exhausts, and I've gone back to the stock fuel injection and ignition settings. Like I told Doug, the last thing I needed was more power, but as he explained, his pipes are designed to smooth power delivery. According to the former AMA Supercross winner, there's a flat spot just off the bottom that makes low-end throttle response feel abrupt; it hits and then falls flat for a split-second before picking back up. His pipe fills in that hole. I went with the basic stainless-steel/aluminum version ($649.99 from www.dubachracing.com), which can be fitted with a spark arrestor screen and quiet-core insert for off-road use.