whats the difference in the main jet, slow jet, leak and needle? Will i need to replace all these when i get my new rossier? Thanks for any help

Short answer is yes, by how much is going to depend on weather you pull the airbox lid off or not, what year of R you have, where you are located, and weather. I would check with Rossier, I'm pretty sure they have a recommendation for jetting with their pipes.

Just take it to a shop and have it dyno tuned that's what I do because I don't have the time or patience to mess with jetting lol. I do everything else myself but when it comes to that I get frustrated real quick and I know it's perfect when it's done on the dyno.

To bad theres no one in Albuquerque that does Dyno on quads