CTE

I have found the Borlas to be great. A very nice low rumble and when you get on it they roar. I have had many nice compliments on the sound.

They are axle backs, and have Ford Racing stamped on them. Easy install.

You should not have to re-tune.

CTE

Vankor

If you go with just axlebacks you definitely don't have to retune, but what about headers and mid-pipe? I'm guessing a tune is in order then, but I've also heard the stock exhaust isn't too bad on the '05+ Mustang so there wouldn't be as much of a performance increase from doing new exhaust.
What did you ultimately pick? I'm looking at JBA LT's and a catted H-pipe. Should be louder than just the Flows I have now, without being too obnoxious.

Lifter583

I have Flows A/T, I had no idea how well they sounded until I stood behind my car while they ran it through a dyno session. I am now convinced that is the only way to decide on mufflers. They also sound much better with the 93 tune over the 87 tune, they also deepened with the UDP and aluminum D/S install. Anything that changes the characteristics of the engine will change the tone.

REDBOSS1

I ended up going with the Brola Stinger Axlback's on AM. They give a nice deep sound and when I give her a cold start there pretty damn loud, I like them alot. I would say they are about twice as loud as the stock mufflers but not the loudest I've ever heard.