I've spent a lot of time on the Rennlist (
http://boards.rennlist.com/) and there is quite a bit of information on the sport exhaust retrofit. Basically, most recommend the DYI'er to NOT hook up the switch and associated vacuum lines and just run the sport exhaust full time. I understand the exhaust itself is a fairly easy install. I just ordered a C4S with the exhaust installed.
Good luck,
Andy