Here're results of my research. From the below awesome videos for mechatronic service on E53, 6HP26x 2004 separator plate code is B051 and for 2005-2006 it's B052. I'm planning to do valvebody overhaul and these videos are detailed.
X5 E53 2004 4.4: https://www.youtube.com/watch?v=Ct8qbmDXqjs
X5 E53 2006 4.4: https://www.youtube.com/watch?v=W7DZbrvrI5k&t=1073s
X5 E53 2004 4.4 https://www.youtube.com/watch?v=YeLFFkx94Jg

And a general guidance on the overhaul. https://www.youtube.com/watch?v=CumnLzqhBao

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'05 E53 X5 4.4i, '97 E39 528, '07 E92 335i, '16 F86 X6M.