I should probably be a bit more helpful - I know that the old 535d and other twin turbo N57 engines seemed to respond well and didn't have issues related to the extra power.
I looked up br-performance and evolve, BR says a flash will take it from 326hp to 400hp and 680nm to 800nm which seems fairly impressive. Evolve say an 80hp gain but don't list torque, so it seems up to about 400hp should be about right.
https://www.br-performance.be/en-be/...00-xdrive-40d/
https://www.evolveautomotive.com/evo...ription_tabbed