Okay - so I waited double the recommended time for my plug change but did my research and went w/ the manufacturer recommended copper plugs. Here's the strange part. I bought the truck certified used w/ 3700 miles and when I pulled the plugs (which I thought should be original from factory) one bank had NGK the other bank had Denso. Anyone else have this occur? Any suggestions on whether I should go back to Toyota or have any recourse?Should this cause elevated concerns? Thanks to all who provide input.