I went with Vortex true dual w/SS tips. Which needed hardly any mods since the truck came with two cats to begin with. Dunno why Ford would put two cats on it and not go ahead and make it a dual. And to think that my poor truck has been choking trying to push all that air out of that crappy stock muffler, go figure. It sounds really nice with a low quiet rumble at idle and hardly anything inside the cab when driving. But it will roar when you stomp your foot down. I wanted the FLOWS but they are expensive in my neck of the woods.