Manufacturers often produce components that are purchased by a company and retailed under the purchasing company's name. When referring to automotive performance or upgrade parts, OEM designates a replacement component made by the manufacturer of the original component.
Installing OEM parts often protect a vehicle's warranty and will ensure your vehicle does not fail the smog check for an emissions system tamper. Using OEM parts is always recommended.
Will aftermarket headers cause my car to fail the smog test?
Unless the aftermarket headers you purchase and install have an EO stamp, meaning they have been tested by the California Air Resource Board and been issued an Executive Order number, yes they will fail the smog inspection; as a tampered emission component. Exhaust headers, not to mention the entire AIR Air injection system is an "emissions component". Any modification to the headers, intake manifold, or exhaust manifold, including removal of a "Y" tube from the exhaust pipes (if equipped) is considered an emissions tamper. Your vehicle will fail the smog inspection even before the tailpipe exhaust is checked.
Mufflers: The smog test does not test the muffler. However we don't recommend you take the vehicle in for testing if your vehicle's muffler is broken or has holes in it from damage or rust. It may cause the smog technician problems getting the smog machine to accept testing your vehicle.
Smog machines are calibrated in California every three days, and are designed to not allow the testing of vehicles which emit oxygen levels exceeding a smog machines preset limits. In other words, if your vehicle's muffler has large holes which are allowing oxygen to be vacuumed in with the emissions stream, the test results would have been inaccurate. The smog machine may not allow the inspection to continue and/or fail the smog inspection.
Aftermarket emission regulations apply to all vehicles being operated on California public roadways, including the following manufacturer brands - Acura, Alfa Romeo, Aston Martin, Audi, BMW, Bentley, Buick, Cadillac, Chevrolet, Chrysler, Lamborghini, Daihatsu, Dodge, Eagle, Ferrari, Ford, GMC, Geo, Honda, Hummer, Hyundai, Infiniti, International, Isuzu, Jaguar, Jeep, Kia, Daewoo, Land Rover, Lexus, Lincoln, Lotus, Maserati, Maybach, Mazda, Mercedes Benz, Mercury, Mini, Mitsubishi, Morgan, Nissan, Oldsmobile, Peugeot, Plymouth, Pontiac, Porsche, Rolls-Royce, Saab, Saturn, Scion, Smart, Sterling, Subaru, Suzuki, Toyota, Volkswagen, VW, Volvo.