1996er 4.2l suddenly starts badly???

Hello, friends.

my car ran perfectly, always started after 1 second. He was standing in the garage for a week. When he started, he only jumped reluctantly on the second attempt, then he ran as usual. The airbag lamp has also been shining right since then. that's why I first thought of a marten bite on a cable, but I can't detect any damage.
This condition has remained: no matter whether warm or cold, I have to press, turn off, then leave again, possibly. a third time, then it starts and runs absolutely calm and perfect. no cylinder is missing, no power is missing.
3 months ago, the petrol pump was changed at Audi, can it be that the check valve was not replaced? it feels as if no gasoline pressure can be maintained. Or is there a cold start valve like my 200 Audi that doesn't work?

I was at a free VW car workshop that read out my fault memory, and here came a long list: misigned on different cylinders, ECU mass error, ECU no plus, ECU emergency run etc. But that's all I can do, because it's usually perfect. STG plugs I naturally pulled off and tested, is impeccable, no oxidation.

Where could a mistake be? Does someone know an A8 freak near me who knows electrical engineering, because that's always the crux of things, and I'm just an old school auto mechanic who knows how to handle SCHRAUBEN...

Thank you, Uli