Stock O2-sensor is still in use everywhere except at WOT. It only provides data to maintain 14.7:1 AFR under partial-throttle conditions.
If you want to gather really useful data for tuning and getting optimum power, then you'll want to install wideband O2-sensor after getting a full aftermarket exhaust system. Main bottleneck is factory exhaust and catalytic. With wideband data AND dyno-tuning, you can extract extra power from 300 with just fine-tuning the fuel-maps. As with carbed bikes, EFI bikes have factory set-up with way too much fuel under WOT in the high-end around 12.0:1 AFR
Leaning this out to 13.5:1 where NA engines make most power gets you an additional 4bhp! The PC is great because it lets you make +/- adjustments to fuel-mapping in 100-rpm increments. Such as subtracting 10% fuel at 8500rpm, removing 2% at 9700rpm and taking out 10% at 11000rpms. No way you can do that kind of fine-tuning to yield perfectly flat fuel-curve and major boost in power with carbs.
That's
4 BHP or 13% more power from just a couple of mouse-clicks!!! buwahahahahahahaa