i dont really know how to describe this but i'll do my best, im looking for the cover part that goes underneath the tire fenders. right above the tires, its like a black plastic cover. it looks like its bolted with some black bolts or something. If you guys know what im talking about it would great to let me know where i can find some.

Sounds like the fender liners

look around here http://www.trademotion.com/partlocator/index.cfm?action=getJointLocator&siteid=214264&chapter=&Sectionids=0,2399&groupid=51836&subgroupid=2403&componentid=0&make=22&model=RX-8&year=2005&graphicID=5455120&callout=3&catalogid=2&displayCatalogid=0

okay wait. does the fender liner go around the whole fender? because i only need the front part of the fender and some bolts, because the other part of the liner its hanging down hitting my tire because of missing bolts

Look at that pic its 2 sections the front half is labeled "3" and the larger section is labeled "4" that goes from the top all the way down the back.