Just don't mix. I was about ready to throw my cams out for the constant idle misfire and CE light that wouldn't quit. So today I tried a set of new NGK plugs, gapped to .060". Wow, what a difference. It idles almost as smooth as stock now, and the low speed "light switch" power is smoothed out some too. Amazing what a good spark can do. BTW, my old Champions only had 14600 miles on them, and looked almost new.