Just remembered, Jorge...
The vent line goes through that bulkhead using one of the rivet holes for the gear web stiffener plate where it meets the 902. If I remember correctly it goes through in the second (from the top) of the four rivet holes. Those rivet holes should be pre-punched. The plans show this intersection, but it doesn't clearly show which hole the vent should use. A follow up question with Van's confirmed that either of the top two rivet holes would be OK. After installation, I'd recommend the second from the top as it makes for easier routing of the vent tube.
Does this address your question?