Leave it as it is. The aero kit was made for that look. If you want the all "silver" look, then wait until the face-lifted bumpers come out and go that route. Will cost a lot of $$$, but looks better all one color too.

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2008 X5 4.8
White w/ Black Interior w/ Bamboo Trim | Premium | Sports + 214" | Tech | Cold Weather | Rear Climate | Premium Sound | Active Vent Seats | Heads-Up | Comfort Access | 3rd Row | Aero Kit | Huper Optik Tint | Clear Reflectors