I just had a local shop do a custom exhaust from the headers on back with custom built mufflers and x pipe. all I can say is I've heard them all from the factory ford header system to the ford muffler only, tubbi, and so on. this guy got it right. the sound is so deep and goes through your chest! he as well built me a new front diffuser out of aluminum with stronger supports ( my old one had the stillen extension and ripped right off at about 200 at a top speed shoot out ) all the aluminum is out getting anodized right now so no completed pictures yet. but if you check out this link you can see some of the pics and a sample vid. not as good as the real thing but you can get an idea.
http://www.facebook.com/pages/Unobtainium-Welding/124989210881567
http://www.facebook.com/pages/Unobtainium-Welding/124989210881567