I replaced my serpentine belt back a few months ago and I started getting a low pitch chirp that now has tun into a high pitch squeal. I disconnected the belt and started the engine because the squeal was hard to pin point. With the belt off and the engine running I have the squeal. Now, it only starts after the engine has run for more than 20 minutes and it has reached operating temperature. The odd thing is when you race the engine up the squeal will disappear and even quit. Slowly returning as a chirp, quickly into a squeal. Any thoughts.