I had everything MAC from the engine back on my '88GT, sounded sweet at first but i'll admit it's totally typical sounding, or i guess i should say "traditional" sounding. I actually got really burned out on the
flowmaster sound, but my car right now has 2 chamber flows on it with custom 3 inch exits and 3 inch dumps, and it sounds bad@ss. It does drone a bit though, but that's gonna happen with just about any louder exhaust you can get.
X vs. H rule of thumb:
Xs make more hp less tq
Hs make more tq less hp
The greatest thing i can say about MAC muffler setups is they're super easy to put on, and i mean super easy. I put my headers/H/catback on my '88 in the parkinglot of my first apartment, single handedly with basic tool, first time ever doing an exhaust swap, and didnt even jack the car up on anything, i backed it up onto the curb of the parkinglot (ghetto supreme). Hey, it got the job done. Everything needed to install came with the catback and headers, and i bought the H used. I've since completed 10+ header to tailpipe installs, and i'd rather do a MAC setup that is a full bolt-on installation than something that has to be welded.
Lastly though, when i first got my '88, it was bone stock down to the silencer, and had several exhaust leaks (header flanges were nearly rusted off). When i did the swap, it felt like a new car. Response was totally there, the sound was totally there, it was a 5 speed and running it up to near redline with that new exhaust was priceless