I have an 05 6MT coupe and have noticed it recently a few times in the morning only when it's really cold. Mine sounds like a whistling noise and goes away once it's warmed up. My car is stock as well.

 

Start one of these things up when its -12 and then come talk to me about noises... my car sounds like a diesel truck that is going to blow up..

 

If it matters to anyone, I no longer get whistling on cold mornings since I replaced my serpentine belt last week. Quiet as a kitty. I had 50k on the original belt. Didn't look bad, but I think with its age, it was hard and slippery.