Kevinkay , have you checked the vacuum line that goes to the regulator on the fuel filter. It could be leaking vacuum causing a vacuum leak and a rich mixture, or if the regulator diaphragm is leaking could cause extra fuel to be delivered through the vacuum line. As far as the pressure loss after shut off, if you could install an inline shut of valve (or even a check valve)before and/or after the filter you could try to narrow down exactly where the fuel is leaking back. Pinching off lines sometimes works but not so dependable. What software are you using to check your adaptation numbers ?

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