Well i just found these guys by a performance shop that i goto a few days ago. Just got my Hummer back and wow it is nice. big sound on the outside and you cant hear it on the inside because of some technology they use. i feel def performance gains too. im gonna have them do my stang in a few weeks. just wanted everyone to know about these guys http://zoomersexhaust.com/pv_cat-back_ford.asp is their stang mufflers. check it out :)