The pre facelift has the regulator separate but I think usually comes together as a unit. I thought they might be interchangeable but looking at some pics the preface filter looks like it is smaller!

When I say "separate" I mean that it fits onto the filter. You'll have changed both with your 06.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)