360 Capristo install deleted SLOW DOWN light

Thinking that I needed the common cat ECU upgrade, I started getting the intermittent "SLOW DOWN" light flashing. It only did it on a second start while cold then went away after about 2-3 minutes of driving. In other words, cold start never triggered it and I could drive for hours. If I stopped for a few hours then restarted (cold, not ice cold), it would come up but be very brief.

Anyway, the problem disappeared last week when I had my new-to-me Capristo cat-back system installed. Nothing was touched on the cats. Maybe they were loosened and retightened, but not sure. Either way, the light is gone and the car sounds amazing. I could could only suspect that one of the sensors were loose and was retightened during the install? Any ideas?

For the record, I have the euro-spec OEM headers and factory cats. None of that was replaced.