I will say only buy the Ford Racing headers if you want loud. Really really loud.
I have the factory exhaust on my car because the turbo system is quite loud once you are at WOT, but it is quiet on regular driving. I drove my Dad's car which has the FRPP headers down to Rich and Dennis' last year and I felt like it would be very difficult to drive without acquiring a long procession of law enforcement officials that feel you must be about to do something illegal. :lol They do look awesome though.
or do a freeway pull beside Soroush. Loudest exhaust EVER......REALLY.......What did you just say....I can't hear ANYTHING.