Got 94 f150 5.0. My ac is making a loud like whirring sound when i press the gas and goes away at idle. It sounds like it is coming from the high pressure line. When i hold that line and press the gas with ac on you can feel the line make that sound. What is this?

 

It almost sounds like power steering pump when it is going bad but is deff coming from the high side ac line.

 

It's probably the power steering pump. They're both bolted to the same bracket and vibrations can be transferred to the other. Use a length of hose as a stethescope and listen for the noise.