I do not think there is such a thing as CARB approved CATS for the TT other than the stock version. At that point there is not point in changing the exhaust.

 

To the best of my knowledge no one builds an aftermarket CARB approved exhaust system for the 996TT. Certification is too costly. Only the factory system is CARB approved. With that said, most good systems with the stock tune file will pass smog test. While there is a visual test, very few if any smog shops care about it. If it passes the sniff test you're good to go.

Mike good to see you back on the board.

 

My setup 2002 tt, k16, epl tune, speedtech X 2.5 with 200 cats - single open quad tips.
On the car three months No Drone ... on the quiet side but has nice note. Intention was no drone on the street with "my current set up".
If I make changes to power - turbo upgrade - so on.note and drone may become noticable.