I have a 2005 4.8is. I do not have running boards. My X came with the flared rear wheel arches. (They stick out wider). The front wheel arches are flush with the body and, in my opinion, don't blend well with the rears. I have searched but haven't found a picture of an X with wider wheel arches on the front.

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2005 X5 4.8is
2002 E39 M5- sold
1995 E36 M3- sold