I'm not aware of any idle/vacuum connection. X5 uses DME to simulate the concept of vacuum idle control as far as I know.

Get some fuel trim numbers and go from there.

My fuel trims went to pegged max when a pre cat sensor heater died. You need to figure out what your fuel trims are

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)