DPFE on 1999 Ford Explorer

I had the DPFE sensor replaced in Nov and my check engine light is back on. So I took it in to a mechanic to diagnose the problem. Again the codes came back PO401 & PO402, indicating both insufficient and excessive air flow problems. They have infomed me that the DPFE sensor has to be replaced again! I understand that it is under warranty, but I would like to know why do I keep having this problem. It seems to me that the check engine light is always coming on for one reason or another. Is there something I can do to eliminate this problem. Please keep in mind that I do not do car repairs, and as a woman I need to get you guys to help me out.