Increase in MPG/K&N

[dcurzon]

People on here say that the fazer runs rich so putting in a more free flowing k&N sorts that out, which you have shown in your MPG
What I want to know is why did they tune it to run rich, there must of been a good reason, so by fitting a K&N are you not "braking" what the factory made.
Ive only just changed my filter at 16,000 miles to another OEM one, and didnt notice any difference in performance, do not know if the MPG was affected or not, as have not checked.
Not sure wher you got the 6000 change filter from I always thought it was 12000

i was guessing the filter change service life... i have no idea what it should be