This is always the second question just after the "how much horsepower am I going to get" question. 

...STAINTUNE exhaust systems are developed from a stock configured bike for real world street riding conditions, rather than full-throttle riding on a heavily modified race bike. Remember that every bike always starts out as a stock bike. 

Re-jetting or chipping is not needed with STAINTUNE exhausts. In most cases, you could actually re-jet or chip your bike with the stock pipes and find an increased result. How is this possible? It's due to the governmental restrictions placed on bike manufacturers to make the bike legal for sale in the U.S. market. If the manufacturers could cut loose and do anything they wanted, the jetting would already be spot on. 

...STAINTUNE exhausts are developed using bone-stock factory bikes. They will get a baseline dyno run and see where the bike is already good and where there is room for improvement. Their hands are not tied by governmental regulations. The result is a pipe that puts the bike were it "can be" rather than "where it is told it has to be" to meet the regulations of the DOT or EPA for sound and emissions.

Please bear in mind that modifying a bike's emissions in any way is illegal in some regions.