The Subaru air pump system is one of the most problematic parts of the late-model EJ motor cars. The solenoids often seize up and fail, throwing "check engine" lights and causing the car to run poorly. Or perhaps yours went missing during an air pump delete install.
Fits all 2008-2014 Subaru WRX, 2007-2009 Legacy GT/Outback XT, 2009-2013 Forester XT.