370D greasy soot in intake manifold - normal?

[nepa]

I,m the guy who still has not started his 370D. In my last post, I stated that I was going to put in fresh fuel with cetane boost and half can Restore to try to improve ignition and compression without tearing down the engine. I pulled the tractor started with my Kubota and let the engine run for 2 and a half hours. It ran smoothly and had plenty of power to get up hills in highest gear. But it still will not start on its own. Cranking speed is good - much better than the videos of engine shown with 16 pages of replies. It just cranks with puffs of black smoke without catching. I have not yet purchased a compression tester but I am pretty sure that I will find that it is at least marginally bad.
I pulled off the big rubber hose to the intake manifold. The inside of the hose and metal intake manifold had a heavy coat of oily soot. Is this normal for a diesel? This tractor has two rubber hoses - one from the filter to a midpoint above the engine and one from that point to the intake. When I bought the tractor, the first one had a big hole from dry rot. Is it possible that a chunk of rubber from the hose got sucked into the engine, got burned up, and is now burned into a deposit on a valve causing bad compression?
I pulled off the valve cover and all but one of the valves had consistent lash of about .010. The odd one was about double. Could this valve have a deposit that leaves a compression leaking gap? Would this cause the oily soot in the intake?