Attributes . Legal in California only for racing vehicles which may never be used upon a highway. Some products may not be legal for sale or use on pollution-controlled vehicles; check your local laws and the manufacturers information.. Because of possible clearance issues, some aftermarket exhaust systems may require modifications or relocation of their O2 sensor port bungs.. Legal in California only for racing vehicles which may never be used upon a highway. Some products may not be legal for sale or use on pollution-controlled vehicles; check your local laws and the manufacturers information. . Names