NIStune R33 GTR - Manual (Page 4)

Notes on Sensors:
R32 uses a titania sensor. These sensors don't produce a voltage themselves - they're resistive. So
resistance changes between rich and lean. This type of sensor produces a voltage of between approx
0V for lean to 1V for rich.
R33 uses a zirconia sensor. This type of sensor produces a voltage of between approx 0V for lean to 1V
for rich. When running these sensors with an R32 ECU you'll find that they still work but the voltage
range is different (read lower). The lean/rich trigger voltages must be adjusted using NIStune. Monitor
the voltages in NIStune and adjust the rich/lean trigger voltages as required.