I've been having the same problem with the secondary air flow. I was recieving both codes (p0491+2) then just p0492. I did the pump test by unpluging the hose and starting the car. I felt the air coming from, so I'm assuming that the pump is good. Don't want to take it to the shop for something I can fix myself. Right now I have both codes again. Could it be the Air Pump Control Valves?