Preheat oven to 350°F. Coat a Bundt or angel-food cake pan with canola cooking spray.
Combine the first five ingredients in an 8-cup measure or medium bowl; stir to blend well.
In mixing bowl, beat margarine, sugar, sugar-substitute, maple syrup, and cream cheese together. Add egg and egg substitute 1/4 cup at a time, beating after each addition.
Add pumpkin and vanilla and beat until combined. Beat in the dry ingredients on low speed just until combined. Transfer batter into prepared pan, smoothing the top with the back of a spoon. Sprinkle chocolate chips over the top, if desired.
Bake until fork inserted into the center comes out fairly clean (about 60 minutes). Cool cake in pan on rack for 20 minutes. Turn out onto a rack and cool completely.