Why a manufacturer would choose to run extremely rich?

Thank you for the replies guys, sorry for the delay.

Cooling the Catalytic makes sense and is something I did not consider.

Andre, I too see this as good news, as room for improvement. I understand that the goals of the manufacturer are to meet regulations and fuel economy goals with a margin of error, I was just digging for other reasons that I may have missed before I try to correct it :)

That being said, I also imagine there was consideration of the fact that the engine was retro fitted with a turbo for a limited production run. Therefore not originally designed around a turbo (low limits).