Has anyone had any problems with VX110 spark plugs?? I have a 2006 and On ocassion one plug will quit firing at idle or low speeds but fires on after 5grand...also it is not always the same plug...It seems to happen more when the ski sits on the trailer for more than 4 weeks...If I change the plug thats misfiring all is good untill next time. I change plugs annualy as a maintenance thing with NGK OEM. I keep the bilge clean and dry all the time. They do not look oil fouled and they are clean and have a good light tan color. Also has anyone tried NGK iridium plugs??? geo