2010 Audi A4 Quattro with 144,000 miles and a check engine light.

What is your question?

Light first on early November 2017 then turned off by itself. Back on mid December. Dealer changed air filter, added fuel additives. Dealer thought to be carbon deposit. Returned car to me. Drove 50 or so miles, light back on. Car has been at dealer since 12/26/17. We've replaced the fuel pump. Light still on. I always use 91 Octane/Chevron w/Techron gas. What's next?

What makes this problem better or worse?

N/applicable

How long has your 2010 Audi A4 Quattro had this problem?

steadily since mid December 2017