whistling/whining noise

The tensioner is automatic so the tension "should" be correct.
How long has it been since a belt/tensioner replacement?

I do both when I change a belt... most times you don't really need to but it's prudent to do so.
(it does feel wrong throwing out something that you can see is still pretty damn happy though )
It's only a spring holding tension, not like a mechanical screw type adjuster, it won't be super tight.
It's just got to stop it from slipping teeth.

As long as you're thinking we're happy with any questions