I think the end chapter will appear this month. Although the new cat was fine on Lambda, the mixture was way off. From memory now, the CO limit at fast revs over 2500rpm is 0.20. I got 0.5+. Way over, even after multiple tries. The only thing I had left was to reinstate the standard ECU parameters, so losing the AR upgrade.
The dealer did the deed. The CO dropped to 0.015 (would need to check, but way below).

The AR exhaust system brings a big improvement without the AR chip, so it's staying that way. Of course, the sooty tailpipe which I had from new is back. But it runs and revs fine.