Fault codes stored in vehicleP2187 (29EF) Fuel mixture adaptation, sum check error P2189 (29F0) Fuel mixture adaptation 2, sum check error 29E7 Fuel mixture adaptation, idling, per time unit 29E8 Fuel mixture adaptation 2, idling, per time unit After a control unit interrogation using a BMW scan tool, we located high additive (5.0 both banks) numbers. The multiplicative numbers were great, both around 1.0. High additive numbers indicate a problem at idle. Since the engine was hot (at operating temperature) we chose not to perform a smoke leak test but connected our monometer (Slack Tube Tester), the crankcase vacuum was very high, (off the scale). We disconnected both vacuum vent valves on top of the valve covers and blocked the vacuum pipes to the throttle body eventually determining bank #1 to be the cause. We removed the suspect faulty bank #1 vacuum vent valve, it was torn (arrow). 
You can buy just the vacuum vent valves (repair kit) PN 11.12.7.547.058 separately (low cost) from BMW. Now the crankcase vacuum reading is normal at around 7.75" of water. We watched the additive numbers recover, reset the fault codes and then test drove the vehicle resetting the fuel trim adaptations.
After replacing the parts we test drove the vehicle and monitored Additive fuel trim. The numbers started to return to normal (0.1). Then we cleared fault codes and reset fuel trim adaptations. | 
