That breather tube goes down into the deepest recesses of the sump. One way to get at it is to pull the bottom pan and there ya go! I removed mine completely due to positive crankcase pressure from the turbo, got real tired of oiling down my left pant leg. 
.....Fretka
I have not removed the hose, or the vent plate/cover it is inserted into, but I have looked closely thru the factory book about this when writing my responses. It does not appear to me to protrude any further than the top plate, and I tend to believe this as if it did go way down inside, it would create problems. It is just a vent. When you say yo got "oiled", did you mean from the other smaller line coming from the airbox that is defined as the box "drain/vent"?
It should have a reservoir at the bottom, near the throttle adjuster knob, and the fuel tank overflow hose, and both the fuel and airbox lines should be plugged below those plastic reservoirs. I understand that when you pressurize the airbox, you will be by all rights, also pressurizing the crankcase with that vent attached, removing the hose where it attaches to the plenum box at the rear, plugging the box fitting, and installing a small vent filter (K&N makes a tiny unit just for that purpose) in the hose, or even installing an automotive PCV valve inline with that small filter, will still allow positive venting of the crankcase without allowing stuff to be sucked back in there. I think plugging the case vent is not a good idea, as it does need venting, if not, you risk seal blowout on all the things that protrude into the engine, such as the cam position sensors, shift shaft, output shaft, valve cover, balancer shafts, etc.
