I ran a set of Magnaflow 14x7x 3 inch in and out on my pump gas street Duster, they where mounted behind the rear end between the 1/4 panel and rear sub frames, exited at the rear bumper I did have three inch pipes straight from the headers to the muffs, no resonators, nice sound at part throttle cruise No droning that I remember, they where a lot louder at WOT I raced that car a lot, it would pickup only .004 ET and .2MPH in the 1/8 mile by removing the exhaust from the headers back, probally the weight saving and not a reduction in back pressure making the gains My next street car will probally have a set of Ultaflow 3.5 inch muffs and pipes on it