if you are hooking up a nos kit to make yourself faster on the street you should think again. Your turboed a6 is a good setup already, just continue to build that motor, swap the head for a y8 head and y8 cam gear, get a p2p ecu wire up vtec, and have it tuned for the turbo setup. But before you put the head on get yourself some titanium valves, springs, and retainers, a 3 to 5 angle valve job then bolt that sucker on I am willing to bet you will enjoy the power. Not to mention you don't run the risk of blowing your motor by using nos. There are so many other ways to improve power before needing to resort to nos.