If you are getting the check engine code PO171 or PO174 do a Google search and it will tell you how to fix it. It is usually rectified by cleaning the MAP sensor, a vacuum leak of some kind or a fuel filter that needs replaced. I would try that first... I went through the same deal with a 1998 Explorer, in fact I replaced both cat converters and a month or so later had the same check engine codes again. I did the Google search, bought some electrical cleaner and cleaned the MAP sensor. I have not had the check engine light come back and have almost 1500 miles on it since plus it runs a bunch smoother.