Place popcorn and pecans in a large bowl; set aside. In a large heavy saucepan, combine the sugar, butter, maple syrup, corn syrup and salt. Cook and stir over medium heat until a candy thermometer reads 300° (hard-crack stage). Remove from the heat; stir in maple flavoring. Quickly pour over popcorn mixture and mix well.
Transfer to baking sheets lined with waxed paper to cool. Break into clusters. Store in airtight containers.
We recommend that you test your candy thermometer before each use by bringing water to a boil; the thermometer should read 212°. Adjust your recipe temperature up or down based on your test.