FOR CAKE: Heat oven to 350. Grease a 9x13 pan and set aside. (you can use cake pans or make as cupcakes too - just adjust cooking time).
In large mixing bowl, combine cake mix and baking soda. Add pumpkin puree, eggs, water and oil. (You can omit oil, but I add it to make the cake extra fluffy and moist). Beat on low speed until thoroughly combined. Beat on medium speed for about 1 minute. Pour batter into prepared pan.
Bake 35 minutes, or until a toothpick inserted in the center comes out with just a few crumbs. Allow to cool completely.
FOR FROSTING: Cream together butter and shortening. Add maple syrup and extract. Gradually add confectioners' sugar and thin with cream until light and airy. Add more cream/milk/maple syrup to thin frosting to the consistency you'd like.