Timing chain or exhaust manifold?

I see the confusion because that does sound like a chain slap but the fact that it seems to go away when you raise the RPM but not start slapping again until you start to level the RPM out again points to an exhaust leak.

I would suggest one of two things. Use a stethoscope or a long screwdriver to touch all around the timing cover and see if the noise is loudest there or at the manifold.

Using this tool will remove pretty much any doubt as to where this noise is coming from.

I attached a picture of it below. Let me know if you have questions but you can pick these up at pretty much any parts store so let's start with this.

Thanks

You are welcome. Keep us posted on what you find.

One more note that I thought of, when you are searching for the noise, the metal of the tip of the scope and the metal of the exhaust or timing cover are going to translate the noise.

So, you don't need to touch the exact spot of the leak or noise. It will get louder the closer you get to it. So, this is about trying to find the area of the engine it is loudest.