Is the noise coming from the IHKA unit itself? If so, try cleaning out the vented areas on both sides of the unit. I used some of those GUM floss brushes with some compressed air in a can as mine was filthy. There is a fan behind one of the vents (I think onvthe right side) that can get dirty and become louder than normal.

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02 Imola on Black Dinan S2 4.6iS
00 RoyalRot on Sand/Black 740i Short Sport