I have a GIAC ECU and AWE exhaust. The damage to a differential is not necessarily immediate. I doubt it would fail from 1 run but after multiple pre/post mod runs I think you would have problems. If they actually ran your car they would have noticed the front and rear rollers were turning at different speeds, which would have been an issue for them to interpret. People who have run awd cars on such dynos have found lower numbers than expected due to to the speed differences.