This is just a guess.
When I was taking long left turns uphill at high speed near oil change time, the check engine light would flicker. It turned out to be loss of oil pressure from all the oil in the pan being pinned to one side during the turn. I would guess that you are having an oil pressure drop after you left off the gas, and that is causing the flicker. Just a guess though. A similar thing happened when I had to hit the brakes hard from a high speed. Hope this helps.
When I was taking long left turns uphill at high speed near oil change time, the check engine light would flicker. It turned out to be loss of oil pressure from all the oil in the pan being pinned to one side during the turn. I would guess that you are having an oil pressure drop after you left off the gas, and that is causing the flicker. Just a guess though. A similar thing happened when I had to hit the brakes hard from a high speed. Hope this helps.