Oil up in the air inlet tube and box in front of the throttle bodies, has to come up the two hoses that run from the cam covers, on each side of the engine.
Why? there is too much pressure in the crankcase from piston blow-by. This pressure is normally releived by the PCV valve and the two breather hoses. One, both or all would have to be restricted or blocked, to push oil up to the air box.
The two cam cover hoses run to the air box, one on each side, but they don't enter there. They run through a small passage, in the bottom of the box, that joines the two together. They are then vented through a restricted hole to the air tube. This is where they can get blocked to build crankcase pressure.
Harvey.
