Not torqued, and no gasket (plug) Cylinder and piston look good. I cannot tell on the last image if that is a valve, or it's condition.Plug is firing, I believe it should have gaskets

 

Perhaps my camera wasn't looking at the correct angle? Plug valve would be at the top of the chamber?

 

Are we able to tell anything from this image at the top of the head?

 

Last image looks like the top of the piston, rotate your optic 180 deg from that, look at the top of the head

 

I just got a few here. Not sure what I'm looking at

 

Last one looks like a partial of a valve seated. If you can get lower in the cylinder looking to the top

 

I see it now. Is the 1/2 circle on the left side showed the valve is gone? It is going to be hard to get the camera to point up...

 

I got some burnt marks on the opposite manifold chamber. Is there a relationship?

 

Are you sure about the compression test?

 

I wished I took the compression test myself before taking things apart but I didn't. I just take the words from the Indy shop for no compression on one cylinder #4 and dealer words for needing a new engine.

The only noticeable issue is with engine shaking and that could also be from ignition: plug and wire. This is why I'm pausing here to make sure of the right call. I really appreciate your inputs.