For me the question is... Will the car pass the inspections?
Around here they measure CO and lambda @ idle and (I think) 2500 RPM @ standstill.
So unless the off-the-shelf cat is slowly killed by me doing AFR 22 they will never find out.
My stance is this: With all the crappy diesel cars around here, I will happily spew out NOX gasses all day long without feeling guilty. Makes no difference whatsoever.
If inspection standards were up, I would probably care more. Because that would mean they would also catch said crappy diesel cars and actually improve on our air quality.
/Allan