[IROC]

Are you getting a P0420 code? From what I've learned on my Tacoma, a P0420 code ("catalytic converter less than efficient" or something like that) is a result of applying CA emissions standards to the other 49 states. In other words, cat operation that is somewhat less than what is considered good for CA is just fine for the rest of the country. It's a non-issue on 49-state vehicles. I've heard second-hand that Toyota dealers even tell people not to replace the cats in this situation.

Also, I've read that you've pretty much got to use Toyota cats. Anything else will simply result in more P0420 codes.

I bought a code reader (they're cheap) and just reset my P0420 when it pops up.

Now, if you've really got a bad cat, that's a different story, but even then I think you're looking at biting the bullet for the Toyota cat.