Which of the following is correct regarding aftermarket catalytic converters?

Aftermarket catalytic converters must adhere to specific regulations to ensure they meet performance and emissions standards. The requirement that they must be CARB approved is crucial, as the California Air Resources Board (CARB) sets strict guidelines to limit emissions from vehicle exhaust systems. This approval indicates that the aftermarket part has been tested and found to comply with stringent environmental regulations.

Additionally, it is essential that the aftermarket catalytic converter is correct for the specific vehicle to ensure proper fitment, efficiency, and compatibility with the vehicle's emission control system. This means choosing a converter designed for the make, model, and year of the vehicle is critical to maintain compliance and performance.

Furthermore, there needs to be the same number of catalytic converters as specified by Original Equipment Manufacturer (OEM) standards. If a vehicle was designed to have two catalytic converters, using only one aftermarket converter would likely lead to subpar emissions performance and could result in failing a smog check.

Thus, all these points highlight the comprehensive requirements for aftermarket catalytic converters, underscoring the importance of compliance with both CARB regulations and OEM specifications.