A few people have been scammed on the site, Only use paypal to pay for items for sale by other members. If they will not use paypal, its likely a scam NEVER SEND E-TRANSFERS OF ANY KIND.
Would it be possible to replace the narrowband O2 sensor with a wideband O2 sensor and some cabling reworks to the ECU? I noticed NC uses a 12mm O2 sensor which is not common. It's a shame they built a good efficiency bike but used narrowband O2 sensor.