exhaust questions?

[Stang066]

does having a cat-back with two performance mufflers add more horsepower than having axle backs with two performance mufflers?
Is it louder having cat backs or is it the same as just having the mufflers?
when i get my car Im leaning towards Borla exhaust because of the quality i like the deep sound. I dont want it to be too loud, is borla a loud exhaust? I heard it on borla.com but they have it revving too high. Its hard to tell when idling and in town driving. I really like the tone of the borla though. Anyone have any advice on which combo i should get?

 

[Motorhead6T5]

The stock exhaust is so good on these new cars,you probably won't see much of any gain by going with a full cat back. As far as noise I think it would have no effect but the mufflers themselves.

 

[DarkFireGT]

just for looks. that's pretty much it on the '05's