How's the smoke with the exhausts exposed?

I would love to do this mod, but would be interested to see how sutty it made the back of the car and how much more smoke it produces.

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05 X5 Diesel, Toledo Blue 19's, Panaramic Roof, Sportspack, Bluetooth & Tint...........
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive, well preserved body, but rather to skid in sideways - beer in hand, body thoroughly used up, screaming WOO HOO, what a ride!