So the electrical faults listed well above no longer occur?
In IT, whenever we have a problem, we ask: “What changed?” In your case it was the carbon clean, so your problem is most likely related to that task.
Among other things, you have a few areas you can check:
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Why is your car now destroying a cat? The only reasons I know of are a slow deterioration of the cat material, or FOD running through the engine and taking out the cat. I assume this symptom is brand new, but I would not ignore it. You are correct, cats are engine out procedure.
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Vac leak of some kind - new engines are extremely sensitive to any vac issues. When you do a clean you disconnect all sorts of vac lines. A smoke test will help you locate any potential issues, but it sounds like you found one already.
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Electrical/sensor - like with vacuum, newer engines are also very dependent on good electrics, including voltage and sensor input. The fact that you have so many faults (I did n’t go back and see if the same cylinders were reporting each time - you should do that) would lead me to believe your problem is higher up the food chain rather than a specific sensor or component. (Did you change sparks when you did the work?)
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Fuel - is fuel being delivered correctly to the cylinders (I would put this way down on the list) but since so many cylinders are involved on both banks, I am not sure this is a likely candidate.
Finally, though I have not done it with the C6 S6, you can read values with VCDS that might give you clues as to the problem. There are only 3 things required for any engine to run: Fuel, fire and air. Your problem is with one of them, obviously that is an oversimplification.
You need more data, but the air leak tact is a good one to follow.
Ed