i have resently cleaned out injectors (on a car) that appears like a slight but permanant misfire. the car has a fuel filter.
My old Astra had diesel in it before I got it, used to stutter on a constant throttle and was a bit rough, got the injectors ultrasonically cleaned and it was like a different car. May be worth a few quid on a fuel filter (cheaper if you say it's for a BMW ) and injector clean?
i think its more the owners husband working in a fish farm with ready access to jerry cans. if you know what i mean. wink wink.
Final update; So the garage took a look at the bike, signed it off with a clean bill with the mechanic saying there's nothing wrong with it. Plugged in the diagnostics which also confirmed that. Did mention that shit fuel has possibly got in, so put a bottle of fuel/injector cleaner in with the fuel, and admittedly it's running better than it has been.