I would not throw parts at the problem, if you can avoid it. But yes, you could replace the CAT. But if you have a fueling problsm or an oil burning problem then your replacement CAT coiuld get fouled sooner than otherwise. And the replacements are cheaper when they use less of the precious metals that form the catalyst. You could also go Balto's route of scamming the system. Certainly tempting, but I support the policy goal of the smog testing (which has been successful), even though I do not like CARB's administration of the policy.
I did a detailed write-up on cleaning... Here it is, with citations and videos:
http://ecomodder.com/forum/showthrea...tml#post542998
Good luck!