[Markgase2000]

You will need to do a simple metal finish repair to fix your rust problem assuming it hasnt ate through the floors yet. If its just surface rust you can sand it down to metal again and use a rust primer to seal it. Then you can replace the carpet or you could even use box liner spray instead of carpet this way it can never happen again (rust on the floor) your dillema is common if you have air conditioning but dont always use it and it is raining outside then water will be let in through the heater core area and onto the floor passenger side the only way to keep the water out when its raining is to either keep the defrost setting on or air conditioner these settings close off the intake for outside air so it can recycle the air. Im sure others have had this problem ive seen it alot myself in Chev/Gm's.