[DanG]

The first thing I do when I get an O2 code is erase the damn thing. It is likely never to return- I've gotten errant codes that never came back.

If it comes back, and it's consistently a specific code, then it's time to get to work. If you do not want to go with the header route, then replacing of your downstream O2 on the offending bank is a good idea.

If you still get the same code with the new O2, then you're outta luck and the manifold (with its defective catalyst) has to be replaced.

DPFE sensor is a $40 part and can be replaced by a fairly novice individual. It's position under the EGR valve makes it somewhat of a pain to get to, but it's only 2 bolts, a single harness, and 2 hoses that plug into it. Don't get the hoses mixed- It uses the pressure differential between the two to determine EGR flow.