That's what I have on my ride. It's pretty quiet. It's loudest in the 1600 to 2250 rpm range, so if you blip the throttle in a parking structure it makes people look.
On the open road, you do not have to raise your voice inside the vehicle to carry on a conversation. It's a very conservative exhaust, because Ford would not allow anything too radical. I honestly noticed no performance gain from the exhaust, only the sound.
A stock Mustang GT is louder than the XP8 Borla setup