It would be better if you could pull the vacuum line(at the manifold) to the fuel pressure regulator and observe the rail pressure to be sure. And of course check the vacuum line to the regulator as well for leaks. Think you did that already but not sure ??

As far as the rough idle I would agree that is probably something to do with what you did when changing the CCCV. Did you replace vacuum hoses as well? maybe one of the hoses to the vacuum distribution manifold broke or cracked or doesn't fit properly?

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