I found a very helpful link to an explanation that helps understand the difference between the OEM 986 exhaust and a modified performance exhaust system (in this care, the Fabspeed Maxflo system):
http://www.fabspeed.com/videos/Boxster%20986%20Maxflo%20Muffler%20Explanation%20V ideo.wmv
This may be pretty basic for those of you who have a lot of experience with these mods, but it really helped me understand the differences between the OEM system and a performance system. Thought I'd share the link for anyone who is researching an exhaust mod for the first time.