I just installed a mangaflow x pipe with cats on my gt. I had dynomax bullets welded in and dumped. It has more drone than my last setup which was the stock h pipe and 40 series flows. But it sounds awesome, it has a nice rumble at idle and then screams at WOT. At full throttle it has a slight whislte type noise, which people refer to as the raspy sound of an xpipe, it took some getting use to. It kinda sounds like ive got a supercharger under the hood. Either way it turns heads, and it feels like i gained some power down low and up high. I think the x pipe also gives it a sound different than most mustangs. Ive already pissed off some neighbors with the noise, i could imagine how loud an off road would be. But i know some mustang owners who have gotten pulled over and fined for not having cats, so it also depends on where you live. Other than that i was thining about just doing an off road then changing it when smog times comes around. But theres always that chance ill get pulled over by a cop who decides to see if my car has cats. Besides, the off road would probably be way too loud, which isnt always a bad thing. The basic rule is if you use a x pipe, get a straight through muffler like magnapacks or bullets. If you use an h get a chambered muffler. However, i wonder how loud a h pipe would be with bullets, i bet it would sound nice still. With a straight through muffler though, you will either have to get rid of the catback or get a muffler shop to weld up something for you, because your catback is designed for a muffler with a offset inlet and outlet. I might try getting tail pipes back on but for now im happy with the dumps off the bullets. Let me know what you decide on and how it sounds.