O2 sensor is connected and seems to be working ok.
Running GTX3 oil.
Fuel economy is still good (500k per tank).
The annoying bit is it gives a slight cough every time you bring your foot off the throttle as you pass over hills etc. That is why I though it was running rich at this throttle setting (ie 5% or something)
I take it there is no adjustment for CO2 etc on these?