Here are photos of the PS8-02 9298 BOOST SENSOR 1989 on my FJ1200 California. I found the wire harness was unplugged .
Prior posts from Pat Conlon (http://www.fjowners.com/index.php?topic=7875.0 (http://www.fjowners.com/index.php?topic=7875.0)) says that the hose is a vacuum line that should be connected to the intake manifold port on the #2 carb.
(http://fjowners.com/gallery/7/3934_26_05_14_10_59_13.jpeg)
This is just for reference since I did not find the Boost Sensor in my Clymer Shop Manual. I think it is called "Pressure Sensor" on the electrical drawing.
The Boost Sensor is located slightly behind, below and to the right of the head lamp.