California Air Resource Board is basically a bunch of tree huggers who approve aftermarket stuff for emissions: Exempted parts are add-on or modified parts that have undergone an ARB engineering evaluation. If the part or modification is shown to not increase vehicle emissions, it is granted an exemption to emission control system anti-tampering laws. This exemption is called an Executive Order (EO) and allows the modification to be installed on specific emission controlled vehicles. Every Executive Order part or modification has an assigned number that can be verified by Smog Check stations, BAR Referee stations, or by the ARB. Check the link out. Pretty
cool:http://
www.arb.ca.gov/msprog/aftermkt/devices/amquery.php