I just ran into this same thing last week. Bought a re-manufactured steering pump and it had the extra hole in it. Went and looked all over for some sort of plug. Tried auto parts stores, hardware stores, a commercial hydraulic supply store and an automotive hose specialty place. Nobody had the right thread pitch for the plug size. Then checked the forum here. Based on what I found here on the forum I wound up buying another power steering pump from a wrecker off an Eclipse or Galant that had the pressure sensor gauge (temp sensor gauge?) and pulled that one off and used it. Glad there's a group of knowledgeable Montero people willing to share their expertise.