Love my X5, Hate my speedometer: fix?

[Quacker]

I've been happily in love with my X5 for a long time, but I could never adjust to the speedo error (optimistic). It runs almost 3MPH slow over all speeds and then gets progressively worse, the faster I go. I have varified that it is indeed the speedometer accuracy and the trip computer tells the truth. Most of you (if not all) have this problem too. BMW corporate was not forthcoming on an answer, and man-I tried to get them to acknowledge it.

Is there a fix or mod that I can pull to recalibrate it?

Thanks,
Q