Do you only supply NTK L2H2 Lambda sensors? Are there any linearization/characterisitic differences with L1H1 sensor?

The Sensors are L2H2 NTK Sensors which are off the shelf available, you can use the L1H1 but might find the lizearizations needs to be adjusted.
We would recommend sticking with the L2H2 sensors which are cheaper anyway.

NTK sensors are very good with leaded fuels compared to the Bosch range and another reason why we use them.