What a pain in the ass this van has become.
I phoned about half a dozen muffler shops and they are all quoting me $800-$900 for the cats plus installation which brings me just under $1000.00
So, I went out and bought the direct fit system for my '03 which was $480.00 tax in.
Replace the o2 sensor you say, I think you mean o2 Sensor, there are 4 of them on an '03 windstar and at $90 a piece, I do not quite think so.
Will be installing this direct fit system very shortly. Will see what happens. | 
