P1131 Hell!

It seems this CEL code P1131 is giving a bunch of us a lot of trouble! Is there ANYONE that could possibly know exactly what it means and what to do about it????? I was told is was the O2 sensor, replaced it and having the same problems. (I only have one O2 sensor so I'm sure I replaced the right one) Was also told it could be a vaccuum leak, already had that checked out, there isn't one. I just can't keep throwing money away replacing parts that don't need to be. I'm sure I'm not the only frustrated one out there.