drain it and clean everything. Start over.
To be honest any European/German cars I would just lease. 3.0 supercharger are good motor plenty of power, haven't seen to many oil consumption issues. Just a lot of software updates. Make sure it's a Quattro not a front track
...on a side note dose your tank with ammonia up to the 2ppm level ONE TIME ONLY! There is no need to continue to dose your tank once the ammonia is at the 2ppm level, do so will only lead to higher nitrates at the end of the cycle and could actually slow down your cycle. Contrary to popular myth, the bacteria does not need to be fed, it will live a year or more without additional ammonia.
lease return Audi vehicles carry a good warranty. Purchase a certified pre own Audi where it goes thru a 3 page checklist(that I half to do) making sure all software are up to date & service history has been performed. Let me know when your ready, I can try to make some phone calls(Concord Audi, Oakland Audi & San Francisco Audi is I'm working)
Thanks. A year out yet. Just starting my homework. Not sure how to determine her color of choice without being obvious. Need to enlist her friends to spy for me. She's had black for so long I can't imagine her going for that, but a black A6 with black rims would be super sick! Wait, this is HER car..... dang it!