In a very large bowl combine cereals, pretzels and nuts.
In a medium saucepan over low heat, combine peanut butter, maple syrup and butter, stirring until all ingredients are thoroughly combine and have a liquid consistency. Add cinnamon and vanilla, whisking to combine.
Pour the wet ingredients over the dry mix in the bowl. Using a spatula combine all ingredients. Spread the sticky mixture on a baking tray to cool down, taking care not to burn your hands. When the mix has cold, add popcorn and serve.