That is a strange one. Sounds like something shaking around.
Id look for loose bolts. I have a bolt with nut that is at the intake round side connector. It spins in the bore. It can make a shaking sound sometime.
Is the radiator fan shroud multiple parts? If its two parts, are all the nibs pushed and locked in?
Are any fuel lines hitting the intake?
What is the status of the tensioner? The shock (be careful, it can get super hot) and the spring can break. If the shock is good, the spring might break and rattle. Ditto for the status of the tensioner pulley and idler pulley?
Have you used a mechanics stethescope, or a screwdriver, or dowel, and tried to listen to the vacuum pump? The bearings an go bad in there and rattle around. One thing recommended to me was to run with the belt off for a short time to see if noise is coming from something belt driven. This was before GP replacement, tensioner shock replacement, etc., so now the engine is much smoother and quieter, even at stone cold frigid weather (which was the condition for this video):
https://youtu.be/8_0kdJ0oySI