Geeez.. I hate it when I open my big blabby mouth and you guys then say something that makes me second guess the biggest font we got.
Took a look at Rockauto. It'* about as clear as mud. Hopefully Dan'* home today and can peek at his FSM'* or we can find more info.
ACDELCO Part # AFS109
SENSOR,HTD OXY(POSN 1) IN EXH MANIFOLD/CROSSOVER
ACDELCO Part # AFS97
SENSOR,OXY (POSN 2) PRE CONVERTER
In my book what they have here is BS. We only have one bank of sensor. When looking at any scan tools we can see B1S1 and B1S2, the second bank is used in a 4 O2 sensor setup like with most V8'*.
Did a little more research and confirmed that S2'* are the rear post cat sensors. Article I found was about disabling them to pass emissions.