Look for a vacuum leak- the crossover hoses at the back of the engine are a known culprit. Bank one lean can be a bunch of things- not just o2 sensor.

__________________
Dave

'05 325xi
'10 E70 35d
'85 911 Carrera
'66 911 Work in progress
'91 Chevy C1500
'95 Jeep Cherokee
‘18 Jeep JLU