O2 sensor ?

[Primus101]

Here's a quote from NGK I just received from an email inquiry-

Front of Engine – is defined as the side of engine with the belts (rear of engine is opposite the belts).
Longitudinal Engines – Left or Right bank is determined as viewed from the rear of engine.
Transverse Engines – Left/Front or Right/Rear bank is determined as viewed from the rear of engine.

[DocWalt]

The 3S engine is backwards from a lot of transverse setups, which is where the problem lies with "normal" nomenclature.