From what I hear, related to Magnetti Marelli ECUs used on Ducatis anyway, is that the part of the flash memory that contains the map is locked, and no commonly available software tool is able to modify the map itself. The tool I have just adjusts trim, reads codes, etc. Now, Desmoworks, a Ducati performance parts supplier, has recently acquired a tool and the knowledge to reflash a stock, Euro 3 compliant ECU to race specs, or any specs desired, for $400.
So, its likely physically possible to do it, but unlikely that you will find someone who can. My guess is GasGas just gets these production ECUs from Mag Marelli pre-flashed to spec. Since the EFI is open loop, an eaiser solution might be one of the relatively cheap piggy back units like the Powercard, that will let you add % increases in fuel in different RPM ranges. I had one on my VRod and it worked very well.