I believe that that is one of the 4-way pipes. Assuming that this is true, the pipe that goes straight through the rubber pipe is actually aluminum and is u-shaped. Of course, you probably noticed this when it was apart. i doubt this is leaking. The rubber part of the pipe is part of the crankcase/cam vent system. A good deal of oil mist will run through that pipe and be recirculated and burned up in the engine. My guess is that the car got a bit of water in the intake somehow and it drained into that vent. The vent doesn't really have much pressure, as it is under vacuum from the engine sucking in air, so it would be pretty easy for it to ingest air. I'd clean it out and hook it back up and check it in a month or so to see if it is clogged again.