Hi Aaron,
We'll need more information about the black on the spark plug; for instance, is it a dry powder coating indicating carbon fouling, or wet and oily which would be oil fouled. Wet, gasoline-soaked plugs indicate that the fuel is not being burned in the combustion chamber, for example if the engine is flooded or there's insufficient voltage to the plugs like with a bad coil.
Champion spark plugs has a page on reading the condition of the plugs that would be worth taking a look at.
[link|https://www.championautoparts.com/Parts-Matter/automotive-repair-and-maintenance/how-to-read-spark-plugs.html|Reading Spark Plugs Color|new_window=true]
I'll have to leave it up to some of our other contributors to help out with the vacuum hose diagram; I didn't have any luck finding one myself.