I not sure about the rs model, but on the regular agility the main restrictions are the drive boss and the rev limiter on the cdi.
Assuming things are similar on the rs, you need to get a derestricted boss and cut the cdi as the first step.
Once that is done, you can then look into the exhaust and upjetting the carb and even going with a free flow air filter if you want to really get the speeds up.
There is lots of information and even pictures on the forum about derestricting the boss and cutting the cdi - just use the search function at the top of the page.