Q: Screeching chirp noise engine - 1991 GMC K2500

I replaced a screeching belt in my truck a few weeks ago. It was an old, worn out one. But then my truck started a new screech that was different from the belt screech. I took off the belt, spun the pulleys and the tensioner pulley was grinding, so I replaced that. But it didn’t help. I took the belt off and spun the pulleys again. The alternator was screeching, so I bought a new one. And the engine was still making screeching noises. I put in a new water pump a couple of weeks ago, but that couldn’t be making the noise. This screech is more of a chirp than a screech noise, and it will vary depending upon the RPMs. It goes away sometimes when accelerating the car. I had bought a cheap belt, so I better pick up a better brand. That might possibly help. The belt tension is good and so are the water pump, idler pulley and the alternator that is refurbished. My truck has 271500 miles on it and it’s a 5.7 TBI. Do you have any ideas about what might be making the screeching or rather chirp noise?