I did it trough a pro guy who is chip tuning all kinds of cars.
There are several sites you can check out about power gain, and they all come to the same result.
Chipped Up - ECU Remap, Car Remapping, Chip Tuning, Fuel Economy Tuning

UPsolute.com The Chiptuning Company

SM Chip Tuning • Bmw X5 E70 4.8 I 355

Anyway, shortly I will dyne test it and post it here.