I have the 4.6, not the 5.0 but this should be comparable... I have BBK long tubes and BBK X pipe with the high flow cats and borla stingers. My friend has the exact same exhaust but with the o/r x pipe. All of our other mods are the same, just different brands. As far as sound goes, and he agrees, my car with the cats sounds better. His is not any louder, at least not noticeably, but when he hits the higher rpms, he gets kind of a nasty cackle sound, where mine with the cats stays a strong deep growl all the way through. We are also drag strip buddies and I consistantly beat him by at least .6 sec in the 1/4. Maybe im a better driver, maybe the brands of my other mods are that much better (doubtful).... who knows? but what I can tell you is that its not my cats that give me the edge so dont worry about losing a great deal of power over the o/r pipe.