Hell, just pull the o2 and look at it and see if it looks like crap. 60 bucks ain't really terrible for an o2, of course my car will take a 17 dollar o2, but it's a piece of crap, I'd gladly pay 60 to get the one I wish I was running, :-), might be worth trying swapping them, mehbe your cat is bad or junked up? You can always pull an 02 from the junkyard and swap it and see if there's a difference.
The cheapest I can find my o2 is $180. Honda sells them for over $300.
Anyway, SVOBoy makes a good point about the CAT. I had a 2000 V6 Jeep Wrangler that I drove for a little over a year. It was horrible going up hills (I'm speaking of Parley's Summit near Park City, UT). I can understand a 4 cylinder having problems with that route, but not a v6 Jeep.
Then my friend told me that his friend's jeep did the exact same thing. It turned out that the CAT/exhaust was clogged. It was creating extra back pressure and bogging the engine down.