Do modified or performance vehicles pass California smog? A modified or performance vehicle can pass California smog only if every emission-related component carries a valid CARB Executive Order (EO) number. Parts without an EO cause an automatic visual inspection failure, regardless of tailpipe results.

• CARB EO numbers are issued per part, per vehicle application — the correct EO must match the installed part to that specific vehicle's year/make/model.
• Common modified-vehicle fails: cold-air intakes without EO, catback exhausts replacing catalyst sections, ECU tunes without EO certification.
• Aftermarket catalytic converters must be CARB-compliant for the specific vehicle — aftermarket cats without EO are an automatic fail.
• Engine swaps require the donor engine to be the same year or newer than the vehicle being smogged, and all emissions equipment intact.
• BAR Referee program handles vehicles with complex modification situations that a standard STAR station cannot certify.
• OBD-II scan reveals the presence of aftermarket tunes that may have altered fuel/spark/EVAP calibrations.

Per CARB Executive Order certification database and BAR visual inspection protocol.