It's important to realise that the original ignition module is designed to be used with high resistance carbon cored leads of the day, not these fancy new and "better" inductive cored leads. Resistive leads work by dissipating the peak current flow as heat which is lost from the leads never to be of any further use. Inductive core leads work partly by storing some of the peak energy in the lead's internal magnetic field, within the spiral wound core of the lead. This energy is returned to the system after the peak has passed. Back EMF from the coil primary is then fed back to the switching module's transistor, creating added heat where it was never designed to come. The Bosch module is simply better suited to handling increased currents due to it being used with much higher powered coils than those used on stock Land Rovers. As for a LRV8, the later Bosch OEM coil seems to be entirely adequate for the job, so replacing it wouldn't be my highest priority.
Here endeth the lesson.
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