None.....a gear change will not increase an engines ability to produce horsepower, or torque. The gear change makes more available what that engine is already producing and more effectively puts it to the pavement! It only feels like the car has more get up and go, when in all actuality, it’s just making better use of the power it already has. There are no real hard numbers that anyone can give you to describe the change. And depending what exactly is done to the car, each experience will be different.