In a drive force control method for a four-wheel drive vehicle using an estimated drive torque for the control, a delay element is added to a value for the estimated drive torque at the trailing edge thereof. At least one of the plasma jets is a cathodic jet and at least one of the plasma jets is an anodic jet. The data is conveyed in the amount of rotation applied to the spreading waveform before it is transmitted. A maintenance indicator value for each cell in which a fixed object is located is calculated. The insert includes a central body having a fluid diverter extending outwardly from the central body for guiding a fluid away from the wall. A first center conductor is disposed within the first connector, a second center conductor is disposed within the second connector, a third center conductor is disposed within the third connector, and a fourth center conductor is disposed within the fourth connector.