[JP Norton]

Peter, for many years I owned a motorcycle dealer/dismantler/repair business here in the US. When we came across "problem bikes", sometimes (very rarely) we'd switch out specific parts with known good ones, to see if it made any difference.

It doesn't sound like you've narrowed the troubleshoot down, between an electrical or fuel related fault. At this point, I would suggest swapping out the entire FI assembly, and seeing if there's an improvement. Barring that, begin swapping out electrical equipment (perhaps the preferred fault code procedure just needs to be set aside). Once this has been gone through, proceed on to swapping mechanical parts.

Your shop (or the factory) is going to need access to known good examples of these parts. That's where a salvaged bike would be very handy to perform this sort of relatively crude troubleshoot.

I realize you're in Greece and there is a scarcity of vehicles with which to do this. But perhaps a trip to Berlin would help. Maybe the factory would help. But it doesn't help that you've experimented and modified your machine. (I know, you state this problem has been there since day 1)

I know this form of TS may not be feasible, in your case, or that the factory might need to be the recourse for such. But try having your dealer suggest this to the factory, or petition the factory on your own. Here in California, we have what is known as the "Lemon law." (Google for info) Does the EU have such a thing?

Hope this has expanded your options in some way.