ben, that tube that goes from the crankcase to the airbox is a crankcase vent/recirculation tube. as combustion occurs, byproducts are made and some of them get into the crankcase. that tube sucks them into the airbox so that they can get into the intake and be burnt again. if that tube isnt there, they would just vent to the atmosphere. its more of an emissions thing IMO than anything else... but with all that oil in there, it was coming out that hole, and thats why it was getting into your airbox glad to hear you got it all fixed up. PS. if its a foam filter, you may be able to get away with giving it a really good wash, and then a light oiling again.