Return to the lines under the plastic cover on the driver's side.

The highlighted line travels across the car along the front seats to provide vacuum to the remainder of the vehicle's lock system. In the second picture, it can be seen traveling across the car along the driver's footwell nearest the driver's seat.

Disconnect this line from the "Y" connector and connect it to your vacuum pump. Pump a vacuum of 10 to 15Hg and watch for leaks for a few minutes.

If this line shows leaks, it could be anything from a cracked line along this section, to either of your door lock actuators on the passengers side, to the gas door or trunk lock actuators. If a leak shows, the diagnosis will continue on the passenger's side of the car.