Plugs have a heat rating. The colder the plug the more heat it can handle. Nitrous and boost cause more heat. If the plug is not cold enough it will burn off the electrode. On the flip side if it is too cold it will not burn off the excess carbon and foul out. Picking a heat range is critical. Split fire to my knowledge does not make a plug 'cold' enough to handle nitrous. I knew a guy who ran those on a turbo and it screwed it all up. Think NGK.
