For those of you interetsed, I recently( for the third time, lol) changed up the exhaust on my 2V 5.4. I was using Magnaflow's cat-back kit #15749. The system used an 18" SI/DO muffler and mandrel-bent 2.5" dual tailpipes. I was happy with the sound, but it wasn't quite loud enough for my taste. I don't like the way the Slowmasters sound of the 5.4s, and I wanted to keep the performanxe of my Magnaflow. I did some research and found that Magnaflow makes an 11" DI/DO muffler with an internal X-pipe. I've never seen one of these or heard of anyone using one, so I was a little hesitant to try one out. I did, and I'm glad I decided to try it. I had my one local "good" muffler shop cut the Y-pipe and run 2.25" pipe ( was supposed to be 2.5", guy claimed he forgot when I noticed) into the new 11" Magnaflow, and keep my existeing 2.5" tailpipes. The sound is now great. It is probably twice as loud as before, with an even better sound. It is a very unique sound with a distinct tone, but with kind of a Mustang quality. It is actually a bit louder than I anticipated, and would probably go with the 14" muffler if I did it again. When towing in third gear at 2500 RPM you know it is there, but not obnoxious. As loud as it is upon acceleration, there is no drone at any speed (unless towing). If I were to compare it to a standard 40-series Flowmaster, I'd say it is a bit louder, but not a whole lot. I'm very happy and would recommend the muffler to anyone.