I was just informed by my dealer that there is a recall on the C6. On some (very few) cars there is a need to replace a clamp to secure some coolant tube. Additionally the ECU needs to be updated (on quite some cars) since there might be a problem with the coolant pump for the gearboxoil. This causes it to shutdown prematurely and this will cause less torque and power.
This is covered by audi recall code 24Q6
If your car is tuned you need to contact your tuner for an update...
My car is affected by the pump problem so ill have to contact ABT to check for an update.