You are not loosing any power on the WM50 mixture at all IF you run equivalent boost
As this is exactly the difference you have in torque
7% or so ........
2.25 absolute bar / 2.1 bar absolute
= 1.071 * 331 = ~355N/m
Do NOT touch your timing! if you want to try and pick up a bit of power put your boost back to the fuel only setting !!! and then take up my advice to reduce your injection amount, and IT WILL MAKE MORE POWER ON WM50
Regards