The reason they use may is that it could be a percentage other than they listed but it will it will be some percentage, depends on the vehicle. The stock map is not linear. The reason it is not is to improve economy and make it easier to make the speed changes without heads bouncing off the headrests.

The engine does not produce more HP in sport mode. Assuming those that think the go pedal response is faster, more linear, are correct that will feel like there is more HP.

My sense is Sprint Booster is the most popular but there are several other options that are at other price points because of the list of features are longer or shorter.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas