That's what us Chevy guys like to call AIR injection, the precurser to the catalytic converer. An AIR injection system is simple enough in concept. There is a belt driven compressor that compresses air and injects it into the exhaust port just above the valve. Temperatures are very high at that point, 600-1500 degrees F depending on operating conditions. Ideally, they are hot enough that whatever combustible gasses are still present in the exhaust system will reignite when exposed to fresh air. These gasses include unburnt hydrocarbons, they combust to form carbon dioxide and water. Carbon Monoxide is combusted to form Carbon Dioxide. NOx's can be combusted to form Nitrous Oxide. All of which are realatively inert in every way except that they are considered greenhouse gasses (bullpoop). CO and NOx require very high temperatures to react with just oxygen and the temperatures were not always high enough in the exhaust port as they depended on operating conditions. A catalyst is used to reduce the temperature required for the oxidation reaction to occur to around 500 degrees and the catalytic converter was born.