It's just a grey area. Truthfully we all know any aftermarket exhaust is going to be louder than stock. An exhaust isn't going to allow more emmisions, unless you mess around with the cat.
When we did this install the car was so much louder. 50 state legal yes, but I knew it was illegal and everytime I saw a cop I had to shift to fifth gear and keeps the revs down to a minimum.
http://www.sromagazine.com/home.php?op=go&id=323309