Nope, the car is extremely stock. Old company lease car so I got after the previous owner had it for three years. Even if it had a chip I would be able to adjust the mileage - if/when I find out how

I can check and test most stuff in the list above but cannot change KVBR value.

Edit:
I have read more on this and for E46 cars it is value/key 20 that holds a KVBR (fuel coefficient) value that can be in the range 750 to 1250. E.g. if I want to adjust the MPG up I take:

Current value x (real MPG/OBC readout MPG). E.g. if current is 1000 my new value would be 1154.