Originally Posted by SBT

There's actually two ahead of the turbo:
P/N: 22641AA32A (Front O2 Sensor) - Manifold
P/N: 22629AA012 (Center O2 Sensor) - UpPipe

And 1 after the turbo (with different P/Ns for MT or AT)
P/N: 22690AA69A (Rear O2 Sensor) - Rear Cat (Manual Trans)
P/N: 22690AA70A (Rear O2 Sensor) - Rear Cat (Auto Trans)