Codes po422 and po460

I have a 2001 Kia (http://www.kia-forums.com/#) Spectra that has had the code po422 for quiet some time. I replaced both O2 sensors and still had the same error code. The check engine light would go off at least 3 times a month. Recently a new code came up Po460 and I am loosing power going up hills and accelerating. I don't think the 2 codes are related but I need to get it fixed soon so that I don't cause anymore damage. Any help would be aprreciated!

why did you replace the o2 sensor for a catalyst efficiency fault?

you need to replace the catalytic converter, especially if its running bad now.it's probably clogged at this point.