ahhh.... that's one of the subtle differences between european spec and US/JDM - I believe it's because they use variable current wideband sensors, whereas european cars with PRA ECUs (I think that's right, but ECU is in the garage...) are designed for zirconia narrowband sensors.
The us/jdm ecus, can by virtue of their wideband interface, work in closed loop target lambda mode (the wideband sensor works from about 11.5:1 to 30:1 AFR), whereas the narrowband sensors only work as glorified switches, so they are only any good for closed loop dithering, and the ecu runs in open loop mode once beyond a defined load point.
www.johndry.com/pra_wiring_diagram.pdf - might help.