In TX, it depends on the year of the vehicle. My 87 needs no cat to pass safety and emiasions.
On the subject of a bored out TB making a difference, if you have a high flowing exhaust, intake, and injectors, it'll give you a bit more power in the high RPM range. If you have a bigger cam and better flowing intake and head, it really pays off. If you're bone stock, I suspect just cleaning your old one will have the same effect.
benjy, you just hit a nerve. A pet peeve I have been having increasingly lately on forums. Don't take this personally, but I've got to vent.
Your suspicion is wrong.
Why is it that those of you who HAVEN'T done something are telling us that HAVE done something, that it doesn't work the way we have experienced by DOING it?