The "snorkel thingies" (and I believe that is the proper technical term) cover the back four plugs as well . . . the non-technical term for “snorkel thingie” is ignition coil (I think – or something like that, I am guessing). Anyway, just undo the nut on the snorkel thingie, detach the wires that are clipped on to it and pull it off.

You will need a very long extension for your socket wrench (I put two extensions together to make a long enough one), because the plugs are WAY down in there! If you don’t have a rubber gripper in your plug socket you will never get the things out . . .