Besides the obvious "catalytic converter", and I'm told "PCV Valve" as well (???)... anything else?

Car is a 00 Si...

 

I don't know for sure, but I think it would include the air box, intake arm, intake manifold, exhaust manifold, the cat, and all the sensors hooked up to it.

 

the EVAP canister and the vacuum system also

 

So a "catalyst system" CEL could be any of these? Anything else?

 

try changing your catalytic converter. I had a code 67 a malfunctioning catalyst system. I changed the cat and the check engine light went off. I got a magnaflow high flow cat for 100 installed. they even made a bung for my 02 sensor.try it.Good luck.

 

that code can also mean a misfire, first i would go on the highway or run it hard to try and clean it out and if it doesnt go away give it a tune up if it needs it. if you gave it one recently then change the cat out