I picked up a left over '14 Silverado 2WD 4.3L in WT trim over the weekend. Haven't driven it enough to develop opinions or tips yet, but I've been surfing Silverado forums. In some forums some owners are reporting issues with knock retarding (particularly during AFM?) impacting performance in these higher compression engines that they are addressing with higher octane fuel. Did you observe any unusual timing behavior during any of your runs? Did it drop out of AFM when it had to retard timing?