That's pretty much all wrong andrewynn.
The filter and regulator can't mask a bad fuel pump, the test port is on the rail, that's the part that counts. Testing (pressure) between the pump and filter only would only give an indication of restriction (plugged fuel filter.) Testing at the rail and under load eliminates fuel supply as being a problem.

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