Strong electrical currents can potentially influence the accuracy of the orientation measurement of the Motion Tracker as a current generates a magnetic field. In practice currents below 1 A do not significantly influence the Motion Tracker if the distance between the wires and the MT is more than a few centimeters.
If you are experiencing too much magnetic interference from power cables, consider using twisted-pair wires which will practically eliminate any radiated field. Strong power surges, such as those caused by the ignition when starting an engine, can corrupt the serial communication or disturb the internal electronics.
The MTi series have a feature called Active Heading Stabilization (AHS). This functions needs to be enabled. AHS offers a more accurate heading than the gyroscope integration only, even with magnetic distortions present. Consider using AHS in combination with VRU_General filter profile or the MTi-2/MTi-20/MTi-200 in cases where you cannot solve the issue with strong electric currents or other magnetic distortions.