As to whether I would walk. It depends. I have a 2002 4.6. It has been many years since I have kept a daily driver for more than 3 years. I still can't imagine selling it. If that is the color you want and the X you want, price is at least second priority. First priority, because it was the high performance model is to find out how it was used, if it was abused and how well it was maintained. If you haven't checked prices for similar 4.6s in your region that will tell you how well it is priced.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas