Hi! Check out the do it yourself threads and also,
http://www.grandprixforums.net/what-...here-1507.html
But since you have experience with DSM tuning you probably already know that stuff continue here
http://www.grandprixforums.net/safel...car-17482.html
If you wanna do headers or better flowing exhaust go here
http://www.grandprixforums.net/heade...ead-25922.html
As for the exhaust headers with 3 inch downpipe are good, but if you like quiet and comfortable keep the cat-back stock. The stock cat back does not hurt performance and also since you have a Bonneville you DO NOT have a U-BEND or DOG BONE MOUNTS. So don't worry about that stuff.
Also WELCOME!
