[Dngrsone]

If you look in the Chilton's or the Hayne's manuals you will see pictures of little metal "H" shaped lifter guides... somewhere aorund '97 they went straight to the plastic-only guides (I surmise since mine didn't have the metal ones)

As to how or why your guide broke... either it had a flaw in it when it was originally installed, some foreign object got between the lifter and the cam, or the lifter had a catastophic failure are my guesses since the plastic is pretty sturdy and there shouldn't be much in the way of twisting on that lifter when everything is working as it should.