Get a close up shot of Cylinder #4 please. Kinda hard to tell, but it looks as though you've got an issue there. The carbon isn't so bad, that could actually help with lower cylinder compression numbers. Looking at the carbon on the cylinder walls and around the surface of the block though, I'd just rip it apart and make it minty fresh again.
Secondly, those lobes looking like that would equal oil starvation. Looks like the head is pretty tarnished probably again from oil starvation. It doesn't really look sludgy
Still not as bad as Vadim's was, but now that you've got the head off, you can disassemble it, and take it to be tanked and cleaned up like new again.