I finally fixed my 0512 code. I looked every where I could imagine an O2
sensor could be installed. I each one at every bank LH and RH and the
3rd is on the y-pipe. Nothing on the main cat

Does anyone have the same configuration as mine?

no they have 2 on the stock y pipe, 1 on the front manifold and 1 on the front precat. i suggest you delete this thread since it is pointless

Most of the 99 have 4 but strangely enough my car has only 3.
Mechanic was surprised too.