So an update! It wasn’t the water pump. It appears to have been the pcv vent, although for the life of me, I can’t figure out how it got fixed by what I did.
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I managed to isolate the sound to the front inlet and worked my problem from there. I took off the filter and it got louder. As soon as I put my hand to plug the hole in the inlet for the hose, the noise stopped.
Following the hose circled in red, I disconnected it from the heating element and found the source of the sound there. I also found the wire disconnected from the heating element, so I reinstalled it. Figuring it was probably the flapper/check valve, I reinstalled everything back and when I turned on the car, the noise never came back.
My understanding was the wire that goes to the heating element was the power source only. So now I’m wondering what part of that whole assembly was causing it.
Also, I believe I was feeling suction whenever I placed my hand to block the sound. Does that flapper suck air at idle for vacuum control reasons and blow air at boost or is mine faulty?