ring break in time

no, I have 120 psi. only down ~20% from the others. but I got no fire, I pull the plug wire and I see a healthy spark to a new plug but the idle does not change. I cant imagine a bent intake valve but dang it if I got a crank speed 5 inch deflection on my vacuum gauge at idle. Only last week did I tell my self "man, I've never seen a gauge do that" while looking at the cheater sheet for a vacuum gauge reading.. and now I'm witnessing it. I sure hope its a friggin intake manifold issue. Taking this chain driven OHC head off requires you to pull the friggin water pump! Ill let you all know what the cylinder pressure test reveals. All valves are .012 per spec hot. Cant really tell if one is lower as they are not comparable with a straight edge unless you take the head bolts/valve train off.
Could it be a bad plug? Swap a spark plug from a good cylinder and see if things change.