Kaaz is overpriced & very noisey. Works a treat though & probably worth the coin in a motorsport application. TruTrac is where I'd spend the money on a street car. Quiet operation, almost as good as a Kaaz 2Way in performance measure, cheaper & serviceable. Diff gears I wouldn't worry about unless you are chasing every last tenth down the quarter mile. It will vastly increase wheelspin on the street & render 1st gear unuseable. Long story short, will make it slower on the street, use more fuel on the street & slightly quicker at the motorplex.