Where can I get the recommended Bosch lambda sensor in the USA?
The Bosch 0 258 007 057 wideband lambda sensor is available from several sources in the USA. One of them is Advance Auto Parts that has stores all over the USA. The part numbers are: MFG# 17014, SKU# 18730616. You can order the sensor from them online too.Where can I weld a lambda sensor bung on the exhaust system?
The placement of the O2 sensor is not very critical. It is a heated sensor and its temperature is controlled by the AFR Tuner, so it will adapt to the placement between wide limits. If the sensor is anywhere on the collector pipe near the footpeg then it will be fine. Motorcycle exhausts are too short for overcooling to be a problem and overheating is unlikely to be an issue on naturally aspirated engines.The recommended installation angle is at least 10° inclined from horizontal with the electrical connection pointing upwards. This is to prevent the collection of liquids between the sensor housing and the sensor element during the cold start phase.
With short and large diameter exhausts reverse flow might be an issue at low RPM and low flow if the sensor is too close to the exit. The pressure pulses may bring some air in from the outside and the lambda measurement may be falsified. Putting the sensor at the front of these slipons should eliminate this effect.