I thought you replaced the fuel filter? Does the check valve not come with it or is it purchased separately? I assumed that since you replaced the filter, the check valve came with it. Also, maybe I’m misreading the posts, and I have the older model of fuel filter, without a check valve, but it is definitely not in the tank, but rather under the long plastic guard running under the drivers side.

Sounds like it may be OBE, but you can check the vacuum on any of the lines running to vacuum driven components. Get a tester(Amazon, etc) which comes with a T fitting and some extra hose, then tap into the various lines as close to the end of their respective run as possible. The tool will tell you how much vacuum is being pulled on that particular line. Bentley should tell you how much should be present. Although usually it’s zero if a line has failed.

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee