The jets that come with most kits are usually pretty close to what is needed. These guys do their homework because there is a good bit of competition and they also happen to enjoy making bikes run right. Some, such as Thunderbike, are designed to not need rejetting except to fine tune for other mods.
Once the exhaust system is less restricted, you can gain another 3 to 5 HP by taking the rubber bits out of the airbox and maybe drilling through the bottom of the filter and airbox. This has been covered in several other threads, so do a search for snorkles to get the details. Or, there is a kit available called the Freak that completely eliminates the airbox and gains you some 8 to 12 HP.
