Noob question: What is this thing circled in red?

I was cruising along and the engine lost all power all of a sudden and check engine light came one. I waited 5 minutes and it started fine and check engine light was no longer there. Now the part in the picture is making a high pitched pulsating noise. When I unplug the green connector, the noise stops. Also, now under the rear end (I think the fuel pump) is making a high-pitched squeal while the engine is running.

Any ideas?

 

AIR diverter valve

 

I was cruising along and the car died and lost all power. The check engine light came one, so I waited 5 minutes and it started fine and check engine light was no longer there. Now the AIR Diverter Valve is making a high pitched pulsating noise when the engine is on. When I unplug the green connector, the noise stops. Also, now under the rear end (I think the fuel pump) is making a high-pitched squeal while the engine is running...it is louder than it normally is.

Any ideas? Also, thanks Apeiron for the info.