I used Saleri water pump which I think is OEM. It also comes with metal impeller. I used HEPU in the past in my e46, and it definitely is a good product. Would recommend it over OE.

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Black Sapphire MetallicNevada BrownDark Bamboo e70 X5 xDrive4.8
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Imola RedBlackBlack Aluminum e46 330i ZHP/6MT