I don't have this yet, I am waiting till the summer but I like everything I hear/see with the "Top Speed" exhaust and headers. You can read all about it on the thread
Performance Exhaust and Header for Boxster
I have no affiliation with the company. I can't speak from experience yet like I said but those who have commented on the thread could vouch for it I am sure and I went to their website (a sponsored link to the left and an ebay store) and their prices won't break the bank. Good Luck.