Upstream Oxygen Sensors ( 1/1 and 2/1 )

Upstream Heated Oxygen Sensor Right Bank 1/1:

Upstream Heated Oxygen Sensor Left Bank 2/1:

The upstream oxygen sensors thread into the outlet flange of the exhaust manifolds.
The right side is 1/1 and the left side or driver's side is 2/1, the reason these are numbered this way is because the right bank of this V6 is where cylinder number 1 is located.