Have you measured fuel pressure real time? It's near inconceivable that a fuel filter on an X5 ever plugs up although the pressure regulator is also in the same device. Fuel pump will soft fail and produce less and less pressure before it finally craps out giving you low fuel volume under high demand or even not enough pressure to operate the siphon jet. I've read many threads where somebody was sure they cured their problem with fuel filter to see a month or four later they finally fixed the real problem, the electric pump was weak.

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