Hi Mateus,
Reading through your post I think the problem maybe linked to a couple of things.
1. the Throttle Position Sensor (TPS) may be on the way out or need resetting. These can be cleaned and reinstalled which may help. But in my experience it is best to replace with a new one if it does play up.
2. You may have to do a fuel flow test, this will establish if the fuel pump is capable of delivering the correct fuel pressure when the engine is running. If the results of the test are not good then you may be able to get away with just changing the sock filter at the bottom of the fuel pump pick up, these tend to get very dirty and can block up. If that doesn't solve it then you may be looking at a high pressure filter change which is a lot more expensive. I know on the Stromtrooper website a lot of people talk about doing a high pressure filter bypass mod and installing an external filter, but my personal opinion is this is just trying to fix things on the cheap and may bring with it other complications and possible safety issues.
I know on my bike that I had similar symptoms to what you describe and after fixing the fuel pump and changing the TPS it has run seamlessly for 100,000 Km. For your info I get in the region of 27-28 Km/L, but that is in Australia where the speed limits are relatively low and heavily enforced, so the bike is not ridden hard.
If you do a search through this forum there should be lots of posts regarding both issues which should get you on the way.
Hope this is of some help, and good luck with your endeavours.
