So I started my journey to work with no issues. Car is running great, no odd noises, nothing... stop at the store before work, car was off for about 15 min & when I started it up, this odd whistling noise started... thought maybe it was a vaccuum line or exhaust. Nope. When I turn the car off it takes an extra second or 2 for the noise to stop. Followed the noise & it sounds like it is coming from behind the glove box? Anyone experience this before? The odd thing is if I put it in reverse it seems to stop as well...

 

My guess is cabin blower/fan.

 

secondary air pump?

 

+1 to this. Check the blower motor and filter. Does the noise go away if you turn off the climate fan completely? If so it could have debris and/or mouse signs there.