I have been autoxing for 6 years now. First, don't change anything on your car, just learn to drive it. Currently, your rx8 is B-stock legal. There are plenty of events in the area, just check out the stickies in the autox forum for the schedule. It looks like the next local event is the BMW club in Brooksville. They are a lot of fun, I got 7 runs on a 1.3 mile course last Sunday. I will be there, just look for a gray miata with black wheels if you have any questions.

I/H/E is Intake/Header/Exhaust. You can do a catback exhaust if you want to stay in B-stock.