My blowerer belt still squeeks and its really tight. How can I fix this?

I wedged a baseball bat in between my alternator and my idler pulley, used lock washers and got a new belt. No matter how tight I can get it, it lets out a annoying screech everytime I start it. How can I fix this? Im more worried perofrmance wise because of losing boost at high rpms. Any ideas?

AHA! I was blameing the supercharger belt this whole time and like probably killing my alternator from that bat. I took off the accesory belt today to try that and no squeak. What on my accesories belt could be letting out this noise? Is my alternator dieing of what?