Originally Posted by MikeL
Good question, I'm not sure on the answer but my guess is they are illegal. My reasoning would be that they will move the catalytic converter (even if it is just a few centimeters) and therefore this makes it illegal. Plus changing anything from stock on cars in California can be deemed "illegal" it seems; although rare. Now whether or not you get caught/pass smog checks is another issue. You would most likely pass I would assume, especially on a new Camaro with good maintenance.
Another factor to look at is if the shorty headers you are going to get will have the CARB certification. I'm not sure if any manufacturer has actually gone ahead and got a CARB cert for the shorty headers. Therefore any shorties would be deemed illegal.
All this being said, without a visual inspection you might be able to get away with it. Let me see if I can't find a specific Yes/No on the high flow cats or maybe another member knows.
FWIW (and I know I'm responding to an older post): American Racing sells CARB compliant shorties and I believe Volant and Injen both sell CARB compliant CAIs.