On first blush, sounds like a vacuum leak to me, RB. I had the same problem once and found I had a very small crack in my intake boot, as well as a cracked line from the SAP to the intake manifold. I'm sure lots of others can share their experience as well.

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2003 E53 3.0i
DOB 10/15/2002
Sienna red, Savannah Beige Dakota leather
Type FA53, Engine M54B30

2018 G02 30i
DOB 4/21/18
Black Sapphire Metallic / Canberra Beige Vermasca leather
Engine B46O