A quote from Haynes Emissions Control Manual:

"The air injection system introduces oxygen (fresh air) into the hot exhaust gases when the engine is running. This promotes further oxidation (burning) of the unburned hydrocarbons and carbon monoxide in the exhaust, which reduces HC and CO emissions, respectively the oxygen in the injected air combines with carbon monoxide to form carbon dioxide, a harmless gas, and it unites with hydrocarbons to produce water, in the form of vapor."




If you are talking about this then yes it is. Even if it isn't what you are talking about I would still say it needs to be there and has something to do with emissions.