Engines fitted with regulated 3-way catalytic converters are equipped with a computerized closed-loop feedback fuel injection system using one or more oxygen sensors (also known as Lambda Sonds or sensors). Other variants combined three-way converters with carburetors equipped with feedback mixture control were used. An unregulated three-way converter features the same chemical processes but without the oxygen sensor, which meant higher NOx emissions, particularly under partial loads. These were low-cost solutions, typically used for retrofitting to older cars or for smaller, cheaper cars. Axle-back exhaust systems replace only your vehicle’s rear exhaust section, usually consisting of items behind the rear axles, like rear exhaust pipes, muffler, and exhaust tips. A&nbsp