go from your turbos and join with your main cats. "Only on TTs. The pre-cats are a second set of catalytic convertors for cold start emissions purposes. They are immediately after the turbos in the exhaust pipes. The main cats are sufficient to pass regular emissions tests, so a lot of the time they are 'gutted' or replaced with downpipes, gaining ~10rwhp & decreasing spool-up time, while still meeting most standard emissions requirements." - Taken from Twinturbo.net FAQ Appendix Z page. Your main CATS are sometimes replaced with testpipes if emissions are not of concern. After the testpipes you have your mid section which usually comes with an aftermarket CATback exhaust. If you're looking at doing a turbo back exhaust your looking at about $1300 or more depending on what parts you're getting. 300 for downpipes, 300 testpipes, 700-??? for catback. Don't forget about work, if you're doing it yourself it's free but if you're getting a shop to do it you're looking at probably about $500 more. Good luck.
