Re: What could this be?!?!?!
I heard mine at steady highway speed, only at that speed nothing at idle and nothing at higher rpms.
Clearly not a whine of the SC in my case.
If I had to describe it - it had an almost electronic pitch - I thought something like the radio was going bad.
If the installer over-tightend the idler you could have this issue - that is what was causing several of the bearing failures. (At least, that was one of possible causes of bearing failure)
Maybe you are lucky and it is the intake.