Definitely not, being in Colorado, we have Subarus here like Mustangs are everywhere else, they have a very unique sound with an open exhaust. That brings up another thing, changing exhausts has no effect in the sound of the car, at least not that I have noticed. But I keep meaning to turn off the music so I can better find out.
Full race exhaust does sound slightly different in the game. More of a raw sound with more rasp. Not extremely different but its noticeable.