quiet exhaust

The Dynomax Hemi mufflers are extremely quiet and help produce good power with minimal back pressure. A Pontiac guy did a pretty extensive test a few years back on a Le Mans comparing performance between several mufflers via time slips.The Dynomax Hemi jobs were at the top of the list for quietness and performed better than FlowMasters. I cant find a link to the article..anyone??
Beware, they are large mufflers(18") and my local muffler guy couldnt get them to fit properly in the limited space on my 72 Duster AND get tail pipes to bend fast(sharp) enough to go over the axle for a complete system. He got them on my GTX and Satelitte just fine with tailpipes, but no dice on my Dusters. I run them on the 72 Duster but without tailpipes.
If you want any kind of rumble I think you'll be disapointed, even just dumped before the axle.