I have the Stage 1 tune offered by bawareca. I've put over 10k miles on it in a little over a month. Drove cross country and back over 30+ days, from below sea level to over 8000 feet, crawling along in traffic and cruising at 85 mph and everything in between. Through the super-dry, hot, 100F+ Western climate, the hot and humid climate in the East and through a blinding monsoon and it never missed a beat and drives beautifully.

It's fast, too.

0-60mph before tune:
7.2s @ 381 ft, 7.4s @ 393ft

0-60mph after tune
5.6s @ 306 ft, 5.8s @ 324 ft

These are the two best times out of eight. Temperature was over 95F both days.

The times tell a story but it's really the way it drives amd hits the gears. Passing when it's needed and on ramps are so much fun.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim