Unlike some models (ie my Z4 had a sport button that changed throttle response electronically), throttle response in the X5 doesn't change, but the fact that the engine is often running at a higher rpm in S mode means that it will respond differently when you push the throttle down.

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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