Up through 2006, the X3 used the 225 hp M54 engine. Your 2008 has the 260 hp N52 engine. Software designed for one won't work on the other. You may find software for the newer engine, but I doubt it.

The software raises the rev limit by 240 rpm, so if your shifting issues happen at redline there may have been a difference. That's a joke. I wouldn't expect any difference. The sofware claims to add 4 hp at 5700 rpm, but doesn't say how much it loses at lower rpm. In any case, 4 hp is not significant.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue