Pumpkin Apple Muffins

1. Preheat oven to 350 F. Grease 24 muffin cups, or line with paper muffin liners.
2. Combine 1-1/2 cups whole wheat flour, all-purpose flour, 1-1/2 cups sugar, pumpkin pie spice, baking soda and salt in a large bowl.
3. In a small bowl, mix together, eggs, pumpkin and oil. Stir egg mixture into flour mixture until just moistened; fold in apples. Fill prepared muffin cups 2/3 full.
4. Combine butter, 1/2 cup sugar, 1/4 cup whole wheat flour and cinnamon in a small bowl; sprinkle over muffin batter.
5. Bake in preheated oven until golden and a toothpick inserted in the middle of a muffin comes out clean, 18-22 minutes. Cool for 5 minutes before removing from muffin cups to wire racks to cool completely.