WARNING: This page is about a different car, the 2013 BMW Z4, 2012 BMW Z4, 2011 BMW Z4, 2010 BMW Z4, and 2009 BMW Z4. However, it is still accessible from the selected car via links, so may be relevant.
TIGHTENING TORQUE SPECIFICATION - BRAKE BOOSTER
Type
Thread
Tightening specification
Measure
1AZ
Brake booster to pedal assembly console
E89
M8
Replace self-locking nuts Retighten 1x after 5 minutes on brake booster