Had a similar issue while it was under warrenty, they changed the leads and plugs then, this time though it is different, firstly my HDC warning light came on and stayed on for about two days, then it went off as mysteriuosly as it came on, then the engine started reving for no reason and then misfiring on engine breaking when slowing down, they ran (dealership) a diagnostic and found eight faults on the ECU, these where cleared but then came back, showing (to them ) that the ECU was faulty.
it is a mystery.. they hope to have it ready for Tuesday