Bad 02 sensor would cause that one bank to run poorly and most of the time generate a code. Bad cat would have also result in symptoms on that one bank. Doesn't fit all the symptoms of a vacuum leak I would use propane or carb cleaner to check around the engine, especially the intake and check the air intake tube for a crack.

Can you monitor short and longterm fuel trim?

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