Every 2 years you have to take your car in for a 2 part inspection, first part is visual, any mods relating to emissions and such need to have a CARB exemption number otherwise they are automatically illegal, and the second part is the electronic part where they use a bunch of sensors to test your emissions and such. I haven't gotten mine smogged yet because new cars after a certain year (mine included) don't need inspection for 6 years from model year. Then the every 2 years rule goes into effect.