I just posted about this in another thread. I don't know what GIAC dose to the TCU if anything. I met up with a local guy who wanted to see the difference between his chipped GIAC 4.2 and my vast chipped 4.2 honistly his car felt stock. I don't know about the ECU for the 2.7 but the ECU and TCU Vast offers blow away any other tuning available. Not only that but GIAC has not developed any thing new for the A6 4.2 or 2.7 in years as far as I know. most tuners have simpply moved on even tho there has been big improvement in the hardware for both motor platforms

Pluss the Vast guys are IMHO some of the best in both performance and customer service