ok, what is this plug for??

While looking for vaccum leaks i found this connector over by the coil packs the red are plug wires, green is ac line pressure sensor, and blue is the unknown connector with three prongs and two wires going into it, you can see the blue safty pin thingy there also. If this is for an option, what the heck would go in that area of the engine bay??

sorry thats the best pic i could get out of it, it comes out of the loom with the ac sensor wire.