Ok I'll take a look at the sensor. From what I've gathered I'm looking for a whitish coating on it. I didn't do the exhaust, but I trust my shop. I was wondering why the second would get contaminated and not the first IF it is because of the coolant, which has been the root of every issue I've had with this car in the past year. Or if burning coolant destroys cats, which I'd assume it does.
Edit: Went up to the mountain today...slowly. The cat is definitely clogged, only noticed it trying to climb hills. My worst fear, since it's the most expensive. Here's what I was wondering all along, ripped from some other forum:
3. Oil or Antifreeze Entering Exhaust
When oil or antifreeze enters the exhaust system and contacts the hot core of the converter the oil and antifreeze will burn off leaving carbon deposits. The carbon deposits will coat the core of the converter thus reducing the catalytic converter's ability to convert from harmful emissions into harmless compounds. As the carbon deposits continue to accumulate, the pores in the ceramic catalyst will become restricted and block exhaust flow through the exhaust system. The resulting increased backpressure will result is a loss of power and overheated engine components. Possible causes are worn piston rings, faulty valve seals or valve guides, blown head gasket or intake gaskets, or warped engine components.
So yeah, now to find cheap/creative solutions to this problem. Good thing my emissions is pretty recent...