In a large mixing bowl combine 1 c. oil, 1 15 oz. can pumpkin puree, 1 3/4 c. granulated sugar, and 1/4 c. maple syrup.
Slowly stir in 4 large eggs.
In a separate bowl, combine 2 c. flour, 1 tsp. baking soda, 2 tsp. baking powder, 1/2 tsp. salt, and 2 tsp. cinnamon. Add to pumpkin mixture and stir to combine.
Pour mixture into a greased jellyroll pan.
Bake at 350° for 20-25 minutes. Cool completely
For frosting, combine ingredients in medium mixing bowl and mix 2-3 minutes or until smooth and creamy. Spread evenly over cake.