In a small bowl, stir together the brown sugar, cinnamon, and pecans. Set aside. In a separate bowl, stir together the flour, brown sugar, cinnamon, and salt. Add the softened butter and gently mix until crumbly. Gently, stir in the pecans. Set aside.
Preheat oven to 350°F. Grease a 9x13-inch baking pan. In a large bowl, beat together the eggs, sugar, oil, and pumpkin until well combined. In a separate bowl, whisk together the flour, baking soda, pumpkin pie spice, and salt. Add the dry ingredients to the wet and gently stir until well combined.
Pour half of the batter into the 9x13 inch pan. Sprinkle on the cinnamon sugar layer and then gently spread the remaining batter over the pecans. Sprinkle the streusel mixture on top.
Bake for 45-50 minutes or until a toothpick inserted in the middle comes out clean. Let cool at least most of the way before serving. It is good a bit warm. Will keep several days on the counter.