Not to get in the middle of a good argument, but Greg the site you posted is not the 'official' NGK site. It has a disclaimer at the top of the homepage that "WE ARE NOT NGK SPARKPLUGS USA" (their all caps, not mine).
I think it was posted somewhere else that the official NGK site is NGKsparkplugs.com and they list the IR for an America as DPR8EIX-9.