You're absolutely right about the "sniffer test". Mine won't pass close inspection now and will be very expen$ive to replace if necessary.
Weight loss was negligible-the catalyst is a small portion of the weight of the muffler, and performnce was worse after removal.
I was able to restore performance with a powercommander and a custom re-map, but I would still discourage anyone from messing with the "cat".
Thanks for the greenhouse gas info - eases my conscience a little.