Well I guess I'll be the black sheep
I would get either the Dr.Gas or UPR X-pipe with the Mac Catback . I like the Mac Prochamber, don't get me wrong. I have Mac LTs & 3' Prochamber for my 89GT. But that's the thing, it's an 89, and I think Prochambers sound best on the 5.0s and Xpipes sound best on the 4.6s. Alot of people think that the X pipe is just loud and raspy, it really depends on your catback system how the X sounds. I think alot of people think that because alot of people run the Bassani X with something like a Bassani, Magnaflow, or Borla Catback. This combo does seem to give it a loud raspy sound.
But a Dr.Gas or UPR X is loud, but when you put the Mac Catback with it, it tones it down a bit and gives it an all around good sound because the Mac adds a deep rumble to it. Now you have a loud and deep combo. Alot of people say that after putting on a Prochamber that it sounded to quiet.
Some of the best sounding Stangs that I've heard have a Dr.Gas or UPR O/R X with a Mac Catback. Like the guy in the gone in 10secs video, or Predator03