80stech, good call on the fuel rail shrader valve. Swapped with a different one and response from the tester is much better now.
andrewwynn, looks like my fuel pressure is now behaving similar to your video. Here's a video of mine:




workingonit, I also tried spraying different areas to find vacuum leaks but some places I cannot get to with the spray so I couldn’t be confident. I’m coming to the conclusion that a well-built smoke machine with a still environment to work in is essential. Interesting that the chinese MAF worked well for you. I did not have such luck with them on my previous X5, but that was years ago and maybe the quality has gone up s
ince. I’ll keep that in mind.


X5chemist, video below of my MAF readings but I’m not sure how to interpret them. I noticed residue inside the intake at the DISA port, but nothing wet to the touch. Is that significant?

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2003 E53 X5 3.0i 5MT
2003 E53 X5 4.4i