The Sheerer pipes probably do have a small advantage over the CPI's (according to some of the dyno-comparison posts on Planet Sand). However, the difference is not significant enough to make any noticeable difference when drag racing, because once you are making big horsepower numbers, a couple one way or the other can't even be seen most of the time. Often the 70 hp bike outruns the 75 hp bike because of traction, a fatter power spread, or any other of a multitude of reasons.
The CPI's can be bought pretty reasonably off of ebay, and are also cheaper when purchased new. If you can afford the Sheerers, get em, but the CPI's will be fine too. I'd go with what my wallet told me.
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