Today exhaust systems are made with higher quality materials. There are many different types of exhaust systems in the industry today. Every exhaust system has to come by law with a catalytic converter. Catalytic converters have precious metals in them to clean up the hydrocarbons and carbon monoxide that the vehicle puts out and turns them into water, carbon dioxide and nitrogen. The oxygen sensors in the exhaust system are placed before the catalytic converter and after that monitor the oxygen storage efficiency of the converter. If there is a leak in the exhaust system before the oxygen sensors, the oxygen sensors will not read right and may result in a check engine light issue. Exhaust systems also make the vehicle quiet. They do this by putting a resonator and muffler into the system. All of the components that make up the exhaust system are there to help improve performance and emissions.