This part of the install does not seem to vary much or at all between 96-98 and 99-00. But... any chance you are missing this step in practice and not just in your list of steps? It follows wht you list above. Also is there any chance you have left slack in the cable? In the image below, check by holding the heater valve arm in the closed position and gently pull on the heater cable putter housing to take up any slack. (paraphrasing/quoting the FSM).
Hope that helps...