If the problem is in the carbs.... big if, but that's the way you are leaning..
- float heights: check and confirm both static and active. Make sure vibrations aren't holding the floats open and increasing the fuel in the bowls. Or anything else for that matter.
- synch - won't cause these problems, but should be set for smooth idling.
- pilot screw and idle settings - fuel is different in Europe. You will need to adjust it here for your riding conditions.
- jets: if there needs to be a jet adjustment (quite probable) they are available from suppliers here, no need to go to Germany for Japanese carb parts..
There are many good resources for learning about carb tuning and adjustment on the internet. If you would rather pay someone to do it, call around and get some quotes. There are many great techs locally, capable of helping you.