Hey,
Do a search, there are discussions on the topic. I asked the same question a while back. Basically, my take on it was that it was not anything great. In theory, it was supposed to be great in specific RPM ranges, but in general, I don't think it does much. Search and read the posts and make your own conclusion.
Afterwards, do a search for a Mikuni Pumper carb. I finally broke down and got one for my bike. I bought the carb from XR's Only, and it shipped with the recommended jetting for the mods (pipe, aftermarket airfilter, stock motor) as well as one step leaner and richer on both the pilot and main jets. It works great, I'm very happy with it. The bike starts alot easier, the throttle response is great, the bike revs up quicker, and the lower-mid to upper RPM range screams. I've dumped the bike a couple times since, and she just keeps on purring where the stock carb would have flooded out. It is expensive, but it is really the only way to "fix" the stock carb troubles. Good luck.
