Just remember the programmed catalyst efficiency threshold varies by auto manufacturer. Very high on late model Toyotas. Many Toyota owners complain that aftermarket cats don't last very long. Cheap aftermarket cats are cheap because they usually don't have as much of the expensive catalyst media, so they can't maintain high efficiency as long as the OE cat. So before you replace it, try taking the manifold cat off and cleaning it before using an aftermarket. Assuming the catalyst is not fractured from heat, an overnight dunk in laundry detergent and a rinse works in cases where its not totally clogged from oil consumption, on the edge with a intermittent highway CEL, etc.