I happen to have a full Borla system...and if you are looking for quiet, Borla is NOT the way to go. Even when I just had the Borla mid-pipe and can on...it was way loud. The header, oddly enough, quieted it down a bit...and changed the note a lot.
What can I say? I like the sound. I don't race the car on the street, I don't stare people down who drive other cars, I don't do any of that "race boy" stuff. I am a 26 year old accountant who loves the way his motor sounds. Therefore I bought a loud exhaust.
So if you are looking for quiet, don't get a Borla.
D. Neil Crawford