In medium bowl stir together flour, baking powder, cinnamon, baking soda, and salt: set aside. In a large mixing bowl beat together eggs, pumpkin, sugar and oil. Add the mixtures: beat until well combined.
Spread batter in an ungreased 15x10x1-inch baking pan. Bake at 350 degrees F for 25-30 minutes or until toothpick inserted in center comes out clean. Cool. Frost after pumpkin has cooled.
In a medium bowl beat together cream cheese, butter, and vanilla until fluffy. Gradually add powdered sugar. Beat until smooth. Frost when pumpkin is cool.