Preheat oven to 350 degrees F (175 degrees C). Grease two 9x5 inch loaf pans. In a large mixing bowl, cream together sugar, cream cheese and margarine. Add the eggs, one at a time, mixing well after each addition. Blend in pumpkin; mixing until completely incorporated. Combine the flour, baking soda, salt, cinnamon, baking powder and cloves. Mix the dry ingredients into the pumpkin mixture; stirring just until moistened. Fold in the walnuts. Divide the batter evenly between the two pans. Bake at 350 degrees F (175 degrees C) for 60 minutes, or until a toothpick inserted into the center of a loaf comes out clean. Let cool in the pans for 5 minutes then remove from pans to cool completely on a wire rack.