It seemed to lower the cabin noise a bit on my 4.8i. There is a recall on this if you have a 6 cylinder.

I got mine from FCP Euro with a lifetime replacement guarantee. Won't have to worry about them breaking ever again.

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Black Sapphire MetallicNevada BrownDark Bamboo e70 X5 xDrive4.8
Alpine WhiteCoral RedAluminum f30 328i Sportline/6MT
Imola RedBlackBlack Aluminum e46 330i ZHP/6MT