Why not buy this
http://cgi.ebay.com/ebaymotors/Porsche-Boxster-986-Factory-Muffler_W0QQcmdZViewItemQQcategoryZ33636QQitemZ805 1203343QQrdZ1QQsspagenameZWDVW
and have somebody weld the pipes on it for you? They are 1" pipes from the pipe before the muffler to the tip at the top. That piping can be bought pretty cheaply on the net in manderel J bends and used to make that.
Hell, a first timer could mig it in their garage, you can't see it anyway. All you need is a hole saw.