Newing Audi TT
Newing is a Japanese Tuning that makes bodykits for most of the platforms VW and Audi produces. Maybe the best bodykits they produce for Audi is for the Audi TT. This bodykit includes a front half spoiler, rear diffuser, rear spoiler in carbon fiber and side skirts.
They produce also an exhaust to fit the rear diffuser.
You can see more details here newing-inc.com.