try the injectors with a noid light to see if they are getting the firing pulse from the ECU.

You may also have a fuel pressure problem or the injectors of those cylinders going bad.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)