Almost all VWAG products are conservatively tuned for both model year updates (zomg more power for 2012!) and for reliability. But as is seen with APR tunes on numerous cars a good amount of power can be had and you can stay within stock boundaries of timing, boost and knock control.
The engine on the TTRS is basically one half of the S6/S8 V10 motor and is unbelievably overbuilt. Forged crank, forged pistons, double roller chain, etc. The turbo is a 61mm Borg Warner. The only major bottle neck I with the engine is the down pipe as the turbo outlet to the cat is almost 3 inches, but the down pipe splits to two pipes when passing underneath the car. Audi did do their homework with the exhaust as its a dual 2.5" system.
I've yet to drive one as we won't get them at my dealer until late this year.