In a large bowl combine the Fritos, Chex, Pretzels and nuts. Set aside.
In a small saucepan melt the sugar, butter and corn syrup over medium heat. Let the mixture come to a boil and then boil for 4 minutes without stirring.
Remove the pan from heat and pour over the Frito mixture, stirring to coat evenly. Transfer the mix to a large roasting pan and bake for 8 minutes. Remove to stir and bake for an additional 8 minutes.
Transfer the mixture to a wax paper lined counter and let it cool completely before breaking into large clumps. When cooled sprinkle M&Ms over mix. Store in an airtight container for up to a week.