I've got the Mangnaflow catback on my 2003 Expedition 5.4L. Once the engine warms up, that baby sounds sweet. Not very loud with regular driving, very little drone in the cab. It really purs great. When you hit it, you can hear that baby rumble. Mine is the one in, one out setup. I installed it myself. The hardest part about it is keeping the polished tip and muffler looking nice!!

I hope to do the Magnaflow 3" Y-pipe with a high perf. cat next. Then come some TOG headers and maybe a mild to moderate cam.