I pulled the codes on my 98 Tahoe after the SES light came on yesterday and I get a PO430 code which means that the 'catalyst system efficiency for Bank 2 is below the threshold for the current engine operating conditions". I have determined that Bank 2 is the passenger side exhaust.

There are four sensors under there. I assume all are O2 sensors. There are two before each cat and two after each cat.

What is broke and what needs to be fixed? Sterling GM says $900+, O'reilly's says $400 for the cat and pipe, and all gaskets.(Its all one piece) Bryan Muffler says $200-300 to cut bank 2 cat out and replace with universal unit.

Could it jsut be a fvcked up O2 sensor?

The truck has not been getting the 16mpg (per tank)it usually does. It also seem slightly sluggish.