Great find, Congratulations!

If you change the color of the wheels to something darker you might consider not going with running boards if they are going to bring the silver back. Wheel spacers and/or lowering will fill up the wheel openings and improve handling if that is something you like. My X is black and I think the black grill is the way to go. Some remove the roof rails, not so many do that. Smoked tail lights are a mod that some do. Since there aren't that many 4.8s any changes you make that are easily noted will take away some of that sleeper feature. I do like a black, fairly dark window tint so it all the black blends together but not too dark. I have seen a black X with limo type privacy glass. To me it seemed to detract rather than improve the look.

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