It has never been legal in the US to remove any emissions equipment on any vehicle that is to be driven on the street. Even if it is outside of the smog check window, it still can not be removed or tampered with.
You can't modify the factory emissions output to go below the required output.
People like the Diesel Brothers from the Discovery Channel settled for like $3 million USD with the EPA for selling and promoting emissions defeat devices like tunes and straight pipes.
