A8 Wide Open Throttle Sticking !!!
 

Last night it happened again - with a clear local road and an uphill causeway ahead, I floored the gas and when I lifted my foot it kept accelerating WOT. cruise control was OFF. I hit the brake twice and nothing. It was like the throttle was binding. Is that because the throttle body needs to be cleaned and the throttle plate is sticking when wide open? If there was a speed trap I was double the limit there easily - I think I managed to un-stick it at 80mph. Th dealer billed the prior owner 2-3 times already for cleaning the intake in records, but the dealer also charged him for an air filter that I found to be excessively dirty - prior owner was an old man that never opened the hood and I'm at 67K. 2006 A8L 4.2L

This is one reason I hate the idea of these electrically operated throttle bodies. Having said that, I have an 03 with 215K on it an have had NO issues. I'm certain that any crank case gases get sucked into the intake after the throttle body and therefore prevent them from getting THAT dirty. Inside the intake can get nasty though. I'd take the intake ducting loose at the throttle body and spray it with some TB/Carb Cleaner. Be sure to manually open the throttle valve all the way and spray all around it.

Probably your floor mat..... Because the electronic throttle body won't continue to open if the pedal signal isn't being increased as well. If this were to happen due to a fault in one of the systems the engine goes limp and check engine light comes on.

This is a benefit of throttle by wire

Agreed. Must be some mechanical problem with the pedal as it has double-redundancy and if there is a descrepancy due to a fault it will cut the injection.
Intake throttle itself is not important in this case.
Signal from brake pedal switch will also cause the power to shut off.
Next time, try pulling the pedal up with you foot to make sure it is not down.