Different states have different rules, especially when it comes to cars and emissions. California’s number one rule, don’t mess with you emissions or buy a car that had its emissions messed with, especially the catalytic converter. Removing the catalytic converter is illegal in any state as stated by John Swantson.
Emission laws have been in effect in California since 1966 and the rest of the states followed suit a few years later. It is a common misconception that removing the cats will give you more power, but the power is so minute that it will go unnoticed. It just gives added noise, which can cause unwanted attention from police and can lead to your car being impounded.
Laws continue to become stricter, and California is no longer allowing people to put aftermarket cats on their vehicles, only factory ones. It is common for people to have their catalytic converters stolen because “they contain three precious metals – platinum, palladium, and rhodium, – to mitigate harmful exhaust gases through a chemical reaction” written by Jeff Goertzen in the OC Register.
Without the cats, your car will never pass smog. Altering your engine with factory parts to pass smog each year and putting the illegal parts back on can hurt you and the BAR Certified shop that you went to. Asking a smog shop for a “hot smog”, or to falsify your results, can lead to large fines and closure of the licensed shop as well and it is not worth it for them. Moral of the story is do not put anyone out of business just to gain a minimal amount of speed that will not make much of a difference.