Have a 2000 f150 with a 4.6. When accelerating and about 2000rpm I have a loud screech coming from the top of the engine around the intake, injectors, etc. when you let off the gas it stops but once the rpm’s get up again it starts, thought is was the belt and pulleys and belts but it’s not need help

 

It is possible worn alternator's bearings and create noise. You try removing the belt and turn the pulley by hand to see if the worn bearings is or not. If you hear the noise and the pulley does not turn smoothly, the alternator should be replaced. Hope you solve the problem.

 

Something in the pulley/belt system for sure.

 

X2 Things that go screech under the hood could be anything like, alternator, A/C compressor, water pump. If you do remove the belt check for cracks in the ribbing.
Too many & it's time for a new belt.

 

If this turns out to not be a belt problem you may be experiencing an intake vacuum problem which can sound a lot like a belt squeal. Vacuum should be going down as rpm's go up and when it doesn't at higher rpm's atmospheric pressure can find its way in to the intake which creates the squeal. Conversely although I've never heard of it with these engines, there can be too much pressure in the intake which is finding a place to escape creating the squeal.

 

And if it's an intake vacuum issue your idle will be effected. To high or to low depending how your engine handles air/fuel mixing.

 

Yeah it dose it even with the belt off so it’s nothing with that system