The only way the fuel pressure regulator can provide more fuel is if the diaphragm is shot and then you will fuel going up the vent line to the intake boot, easy enough to check. The other only way would be that somehow the vent line is plugged and pressure is building up in the regulator, or you have that vent hooked to pressure somehow. If I had to throw out a guess I would say MAF. How do you have <5k on the injectors ??

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