This Audi 2006 A6 had an oil leak that was already "fixed" by another shop. When the customer took it back she was told that now the car needs new turbos. The oil leak turned out to be cam plugs and timing chain tensioner gaskets which together with new valve cover gaskets took care of the oil leak. The other shop refunded the money for the original repair.
Torque converter replacement is a very common repair for 2001-2006 A6, 2001-2002 S4, 2002-2004 A4 and 2004 RS6. It usually shows up as a trouble code P0741 (Torque converter clutch performance) and may be caused by torque converter internal oil seal failure. Because the seal is inside the whole torque converter must be replaced. It is important to replace it with improved OEM part. Below you can see what is involved.
This 99 Mitsubishi Eclipse came from another shop after timing belt replacement. The engine had no power and the customer was told that the valves were bent and the cylinder head needed to be rebuilt or the engine replaced. The customer found it hard to believe that the other shop installed the timing belt incorrectly because it was a reputable place :). I had to show him the pictures to make him believe.
Most of first generation (second generation is not available in USA yet) Audi Allroad will have air suspension problem before 100K miles. Most of the time the front air springs will need to be replaced. It used to be a costly repair but recently there is a quality aftermarket replacement and the cost came down considerably. Below 2001 Allroad with about 85K miles in a need of two front air springs.
Are you forcing the first to second shift on a manual trans? The owner of this 2003 Audi TT did just that and with time ended up with broken 1-2 shift fork.