Why does this motor (E338) require NGK BR9EV spark plugs? I called 2 dealers and my manual all said BR9EV. These plugs are $4.50 a piece!! Something to do with a gold electrode I think. When I talked to Hauk and asked him if I could use BR9ES with the standard electrode he said "NO", he didn't know why but he said I have to use BR9EV plugs. I don't understand why. I hope I don't foul a lot of these plugs.