I'm going to describe the problem I'm having as best I can. I'm still learning a lot about cars in general so excuse my noobie car talk please =)

I have an '05 Mini Cooper non-s Manual trans.

First off I seem to have a little fluctuation in RPM when I'm idling in neutral. Seems fine up until highway speeds in 5th. When I ease off gas going, say 70 in 5th, there seems to be a high pitched sound and car feels like it jerks a little bit. It's not so much a squeak sound, people told me that might be problem with belts? It's more of a whistle. There's also very faint sounds of....like metal chafing? Which obviously would be bad. It just sounds like maybe something is loose. Maybe if someone had similar problems or maybe knows what wrong, shoot me some speculations. Thanks guys!