I have sent one of my spare ECU�s to Spiro, it is the first generation -00 that was on my bike originally (2004). One of the ecu�s that had most problems.

Spiros have now extracted the fuel and ignition map from it and made a discovery.

The Ecu used is the same as used in the Aprilia Strada 650 but it is diffrent regarding the maps.
Yamaha has a 20-30 degrees more ignition advance in the area were the XT has the most surging compared to the Aprilia. He will soon send me some screenshots of the ignition and fuel maps.

This could be the reason why it is so hard to make the XT completly surge free as the Powercommander does not change the ignition timing. If this is one of the reasons.
I understand that it also has to do with the fuel tables, but if the ignition timings is completly off it will be hard or impossible to tune with only fuel.

I know that the powercommander for the Raptor 700 has the ignition module so that you can tune the ignition maps. Why is it diffrent for the Xt660 since it is almost the same engine?