Stock motor won't see any benefit to going to an iridium plug, other than longer plug life due to harder metals in the electrodes. If you want to waste that much money on plugs i'l mail you some stock champions and charge you for the autolites irxp's you won't be able to tell a difference in the way the motor runs and it won't make any difference in fuel economy or power that just replace worn plugs with new ones wouldn't do.