Audi A8 3.7 quattro is fully lurking

Hello Audi fans,
I have recently also an Audi A8 and have the following problem:
The engine takes on gas in all stages of the Tiptronics, if I tread the accelerator pedal carefully, so only as far as the engine also gains speed.
However, if I give too much gas (very bad at full throttle) the car does not accelerate any more and the engine shakes.
When the tiptronics is switched by hand, it is not so noticeable. When the engine is given a light gas, it turns up to the speed limiter and then switches to the next driving stage.
However, in automatic operation on D, the accelerator pedal must be further penetrated before overtaking, so that a driving stage is switched down. Now, however, I have to take away gas again, which the engine shakes and immediately switches the tiptronics up again. An automatic overtaking process is therefore far too dangerous, because the necessary power is missing with a little too much gas.

I've already filled Super Plus with 98 octan to avoid knocking. No success.

Since the engine rotates cleanly up to the end with little gas, m. E. something is not right with the air mixture when accelerating or the electronics (knock sensor).

I was also with the vehicle just at the AU, the KAT regulates wonderful (at least the one KAT, since the examiner only tested an exhaust pipe).

Who can think of something like this or have had a problem like this before?

Thank you for every contribution.

Martin E.