To remove the whistling mirror noise from your side rearview mirrors, install some sign vinyl over the folding crack. This will remove the ability to create the whistling noise at 80+ mph. If you need to fold the mirrors, just remove the tape! It doesn't take much to cover the crack and because it is sign grade it is designed for automotive applications, and should remove easily with no residue.

Go to a local sign shop and ask them for a small sample color...most shops have an inventory that is extensive enough you can find some that will match your paint pretty well...or you can just use black....that is what I did...but my car is black!