Preheat oven to 350°. Coat a baking sheet with cooking spray and bake nuts for 10 minutes; remove to cool slightly. Heat maple syrup in a saucepan over medium heat, stirring constantly; bring to a low boil, and stir in butter. Add nuts, and stir until coated; let cool. Combine cinnamon and chili powder (less if you don't want it spicy) in a bowl. Remove nuts from the maple mixture with a slotted spoon, and toss in the spice mixture. Lay nuts on a baking sheet, and sprinkle with a little sea salt; let dry. Store in an airtight container for up to 10 days.