Years ago I picked up NGK BKR7EIX-ll 6988 plugs and Magnacore wires for my SRT6 from Rob, I think. I never got around to putting them in. My NA now has 162K kms and is not idling as smoothly as I'd like. I'm thinking I will put them in it. Has anyone used colder plugs in their NA? Any issues, concerns I should consider before busting my knuckles and putting them in. If I do, should I gap them at .39 or .44? Thanks