Strange chirping sound from car, but it's not a belt issue?

I have a 2004 Ford Ranger and had recently replaced the Drive Belt, Tensioner, and Idler Pulley. However, the noise continues to make a chirping sound. I had removed the drive belt and started the car VERY briefly and still heard this chirping sound (I put it back on afterwards). I am very confused and I cannot... show more I have a 2004 Ford Ranger and had recently replaced the Drive Belt, Tensioner, and Idler Pulley. However, the noise continues to make a chirping sound. I had removed the drive belt and started the car VERY briefly and still heard this chirping sound (I put it back on afterwards).

I am very confused and I cannot find any good answers on what to do now. The chirping will only occur when the car is warm AND idling/low rpms.
Update: 3.0 Liter Engine
Update 2: I'll update this question when I find the solution. So far I'm getting good leads by you guys
Update 3: It was indeed the camshaft synchronizer AND the sensor that went bad. The bearings in the synchronizer were going out and making the chirping noise and replaced both and now the chirping is gone.
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