2003 Ford Mustang squeaky belt

I live in West Texas and we just recently got our first serious cold snap. Anyways along with that cold snap came a squeaky belt on my 2003 3.8 L v6. I used the spray bottle trick and sprayed the belt while the noise was being made, and it did not go away. I next looked at my tensioner which did have a little play in it so I replaced it, and I did check all the pulleys while I had the belt off and they seemed good. Went ahead and replaced idle pulley and put on a new Dayco belt while I was at it. Still a squeaking noise. At this point I was getting a little frustrated so I had my electrical system checked and my battery showed to be bad; maybe the alternator was not charging correctly, putting extra strain on the belt? Anyways had alternator bench tested and while it was in the machine being tested, I could hear a slight chirping sound. There it was, problem solved. So went ahead and purchased another alternator put back on and wouldn't you know chirping sound still there! The car runs fine I am just about to pull my hair out trying to figure out what this could be. Any suggestions would be great!