Engine performance upgrade components often pose smog check problems, however if you can show proof that the units are sold legally in California and possess an EO number, they will not cause a smog check concern. EO stands for Executive Order. This is the number given to the product by the California Air Resources Board certifying that it is emissions legal. Most manufactures of aftermarket performance upgrade components will stamp this number on the actual unit or they will print in the unit's manual, catalog or some other paperwork which pertains directly to the component in question. You will have to present this number to the smog station where your vehicle is being smog checked.
Here is a Link to the California Air Resources Board's Aftermarket Emissions Parts Lookup tool.
If any performance ugrade component you wish to add to your vehicle, whether it be a supercharger, turbo unit, air intake, headers, ect., is not listed on CARB's website, it is not for legal use in California (except for off-road use only in certain circumstances) and it will cause your vehicle to fail the smog inspection.
