I'll give a quick guess while we wait for someone with more knowledge to answer. The Bentley service manual doesn't mention any, and neither does the 101 Projects book:
http://www.amazon.com/Porsche-Boxster-Service-Manual-1997-2004/dp/083761645X/ref=sr_1_2?s=books&ie=UTF8&qid=1392649984&sr=1-2&keywords=porsche+bentley+manual
101 Projects for Your Porsche Boxster
They both have a fair amount of discussion of exhaust systems, mods, etc... and I haven't seen any mention of 49 states.
However I would wait for one of the experts to answer, but my best guess would be no.
Steve