As long as its copper core + 4 heads, its ok?

I asked the technician at the service centre today (sent in the 300SE for a radiator flush and coolant change - insisted on MB coolant), and he said we shouldn't use the 4 headed plugs because they could be an oversupply of power. It doesn't really make sense to me. Why can't we supply more than the required recommended?

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... Kerry

126 tailed by a 203, 129 leading the pack.