The small brass outlet connected to the back of the petcock is the vacuum line. Run hose from this connection to the intake manifold port on the Number three Intake Manifold. The large outlet is Fuel Supply. Run gas line from here to the Fuel Intake port on the carbs. The fuel intake is between the Number One and Number Two Fuel Bowls. Email me direct at: XJ900Owner@aol.com for further important hook-up ideas. Rick Massey