?
The ecu relies on the airflow meter amongst other things to calculate the fuel/air mixture, the crankcase ventilation is further downstream, so if it is not functioning correctly then the ecu will not calculate it correctly, as the extra burnt gasses are taken into account.
This can cause problems, such as the throttle response feeling a bit flat.
I had a problem similar on my A8 a few months back. The main engine breather had collapsed, i couldn't believe the improvement when i replaced the hose.