I used the Borla XS. Here is a noise db comparison of the major performance mufflers. Th Flowtech Warlock, Basani Real Street, Hooker MaxFlow and Borla XS were all within less than 1 hp different on the Dyno. The Magnaflow was within 1.5 hp(on a 375 hp ford) of the leader in hp performance and rounded out the top five, but on the noise side of it all, the Borla XS won hands down with the Borla XR1 not doing as well. That is why I chose it and it has pleased me well. Awesome sound and impressive on a 512 IMO. I like a deep growl, but I hate notice just for the sake of it. Lol. Btw, a few points one way may not sound like much in a db test, but considering there is only 4 or 5 db different than some mufflers to straight pipes, a few db is definately noticeable. Lol
Sound Off in Quietest to Loudest (Decibels):
1.Borla XS, 80db at idle, 90db at 2,000 rpm, 110db at WOT.
2.Hooker Maxflow, 80db at idle, 90db at 2,000 rpm, 120db at WOT.
3.Magnaflow, 82db at idle, 91 at 2,000 rpm, 114db at WOT.
4.Flowmaster, 82db at idle, 93 at 2,000 rpm, 115db at WOT.
5.Flowtech Warlock, 83db at idle, 92 at 2,000 rpm, 112db at WOT.
6.Dynomax UltraFlo, 83db at idle, 94 at 2,000 rpm, 113db at WOT.
7.Borla XR1, 83db at idle, 96db at 2,000 rpm, 118db at WOT.
8.Bassani Street, 83db at idle, 96db at 2,000 rpm, 120db at WOT.
9.Edelbrock RPM, 84db at idle, 93db at 2,000 rpm, 118db at WOT.
10.Bassani Real Street, 84db at idle, 96db at 2,000 rpm, MAX. (120+db).
11.Flowtech Afterburner, 86db at idle, 94db at 2,000 rpm, 115db at WOT.
12.Flowtech Terminator, 86db at idle, 94db at 2,000 rpm, 119db at WOT.
13.Hooker Aerochamber, 87db at idle, 94db at 2,000 rpm, 114db at WOT.
14.SpinTech, 87db at idle, 97db at 2,000 rpm, 116db at WOT.
15.MAC, 87db at idle, 98db at 2,000 rpm, 119db at WOT.
16.No Muffler, 91db at idle, 103db at 2,000 rpm, MAX. (120+db).