That`s the oil feed for the turbo on the 4x4 I think? I believe this is from the block gallery on the 2wd. You have two sensors, one for the dash, one for the ECU. 2wd heads have one in the oval plate, and the smaller bronze one in the side of the head somewhere, while 4wd i think have the ecu sensor on the side in a big drilling, and the small bronze one I seem to remember is next to No.1 spark plug? Where you have the oval plate on the 2wd head, i think this is blank on 4wd heads?(definately on small turbo escos). Hope this helps!!