Originally Posted by donbrew

I am putting money on flex pipe, but anyplace there is a gasket or rubber/plastic hose. If you have removed and replaced HO2 sensors, you may not have sealed the correctly. Holes in exhaust system.

The last time my flex pipe failed I only noticed a noise when the right windows were open when I was driving past curbs with driveway cutouts. Sounded kind of like intermittent cicada noise.

Anyway, the point is : the description/name given for a OBDII code does not usually mean what a guy on the street thinks it means. There are books devoted to OBDII code troubleshooting. NEVER buy parts on the recommendation of an autoparts store code reader, before doing your homework.