The proper torque is built in after a pre-determined amount of stress is applied by the air wrench. A certain amount of twist occurs on the stick to prevent over-tightening and ensuring the correct torque. Today's car is not designed for too much or not enough torque. They should be checked thoroughly for cracking and they should make sure that it is the right kind of wheel for the vehicle. Just because the lugs fit the holes, does not mean that the wheel is suitable for that car or truck.
Improper installation can be very expensive.
Safety should always be the first concern when dealing with wheels and tires. It's not only for the benefit and safety of you and those in your vehicle, but for those with whom you share the streets and highways.