I've owned two vehicles whose catalytic converters were recalled due two a couple of reasons: one being the quality of the CC and the other being a reduction in power due to a material building up and reducing airflow.
The car I own now (2007 Pontiac G6) has had such a recall issued, but only some cars are affected. I feel that sometimes I have less power than I'm supposed to have.
Are there tests for bad CCs? My exhaust pipe is welded on to each end of the CC on the G6 so I can't exactly peek inside.