Most people start with intake, exhaust, and y-pipe.
Check
www.spmotorsports.com for ideas.
KKM is cheap and DIY.
Bassani and Borla are the most popular bolt on cat-backs, but a little pricey
SHO y-pipe - price varies depending on what model you get
Or you could just drop a chip - Super or Diablo.
Try using search in the Performance section to find valuable info. FAQ on the main page is helpful, too.
Good luck!
