Did you listen to what Steptoe said at all ?? Pay heed to his advice, the sage has spoken words of wisdom.
The lambda probes are the same part regardless of cylinder location hence they are interchangeable. Its only an electrical connector to undo and then unscrew the lambda like a bloody big spark plug. Swap them over from left and right side and see if the problem changes between left and right cylinders:
If no different then the lambdas are good. If the problem 'moves' with the change of lambda probes its QED. A piece of piss and all of 5 minutes work for somebody to do.
If you need a new lambda probe, they are available as NGK/NTK parts rather than the same part in a BMW packet for twice the price.
When I had a lower coil fail last year, it killed the Lambda probe on that cylinder probably due to poor combustion/excess fuel.