Preheat oven to 350ºF. Generously coat a 8 ½ by 4 ½-inch loaf pan with cooking spray.
Whisk whole-wheat flour, all-purpose flour,pumpkin pie spice, baking powder, baking soda and salt in a medium bowl. Whisk eggs, pumpkin, oil, maple syrup and vanilla in a large bowl until smooth. Add the dry ingredients into the wet ingredients and stir with the silicone spatula until moistened. Add chocolate chips and stir until just combined.
Spread the batter out into the prepared loaf pan. Bake until the bread has risen and the center springs back when lightly touched, 58 to 65 minutes. Test with a toothpick to make sure there is no uncooked batter in the center. Let cool completely in the pan on a wire cooling rack. Run a knife around the edges before turning out and slicing.
I prefer to use dark maple syrup when cooking. It has the strongest maple flavor. Note that baked goods sweetened with maple syrup have a darker color.
White whole wheat flour can be substituted one for one with whole wheat flour. I like white whole wheat because it is lighter in color and it has a less pronounced wheaty flavor.