When I did repairs in that area I did all the little coolant hoses as well, those that supply the heater circuit. All in all I did every rubber hose.

In the M54 it's a good time to do that as those hoses are usually buried under the parts you are servicing now.

Good reminder on the intake boot, I experienced that too. Which reminded me, you may want to pull your DISA and check that the flapper mechanism is still in good condition. I checked mine when I replaced my intake boot and it was on the verge of failure.

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04 X5 3.0i auto
03 X5 4.6is