California considers any exhaust system modification, before the catalytic converter(s), an emission system tamper. It appears the PACESETTER V6 DUAL EXHAUST ADAPTER KIT is a CAT back system, meaning it is installed after your Ford Mustang's catalytic converters and after the oxygen sensor.
This installation should not cause a smog check failure in California. We recommend contacting Pacesetter technical team at (602) 266-1964 for confirmation. And if need be the Bureau of Automotive Repairs at (800) 952-5210.
