Fuel mixture is controlled largely by the MAF and pre cat O2 sensor regardless of the altitude. However, when the altimeter and MAF readings do not match it can result in no adjustment to fuel mixture resulting in a variety of engine symptoms. The variation in air density and altitude on your A to B trip is well within min/max fuel mixture parameters of the MAF/pre cat O2 sensor and any mismatch between the altimeter and the MAF would not be significant enough to matter in your circumstances anyway.

I don't think the variation on bank 1 has anything to do with the MAF or the altimeter as the variation would be in both banks. I would troubleshoot the pre cat O2 sensor on bank 1 as the culprit.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas