I sit in the passenger seat,aslong as you are quickfingered its fine,whoever is driving needs to understand not to move the throttle(unless they have too due to traffic),i have few steep hills near me and there great for loading,after a few miles of driving at different load and map sites i park up and check everything via data logs,then interpolate inbetween load sites that you are happy with.at the end of the day it still needs to go on the rollers to fine tune and get the most out of an engine.