Muffler change up
I used those mufflers before as well. The interior racket is taken down to a sain notch. Then, I realized I had a stero that also worked!
Heres the "Jegs" true dual exhaust off of Hooker headers on a stock 318 with bolt on's and a small cam.
http://www.youtube.com/watch?v=pOYMlTTecTU&feature=channel_page