2.7 engine whistling noise

My Tacoma just hit 140k and with it came a new noise. I don't think it's anything severe, I'm just so used to my engine's normal noises that it always concerns me when I hear something I've never heard before.

Only notice it on a cold engine. But around 1900 to 2000 rpms, I hear this faint whistle/squeal but more of a whistle. It stays constant if I can hold the rpms in that range. My best guess is throttle body (sounds similar to a noise I've always had when I let off or press the gas on a cold engine) or maybe a bearing in one of the pulleys?

I just changed the oil. Belt 10k ago. Plugs 15k ago. Throttle body was cleaned around 100k I believe? If anyone has a similar noise I would be interested to hear your take. Thanks.