Preheat oven to 350ºF. Coat a 12-cup Bundt pan with cooking spray, dust the inside of the pan with flour and set aside.
Combine cake mix, pudding mix, egg substitute, sour cream, water, oil and vanilla in a large mixing bowl. Using an electric mixer, mix on low speed for 30 seconds until dry ingredients are moist, about 30 seconds. Then mix on medium speed until batter is almost smooth, about 2 minutes; fold in chocolate chips.
Pour batter into prepared pan and level the surface. Bake until a wooden pick inserted near the center comes out clean, about 1 hour. Allow to cool in pan on a wire rack for 20 minutes; invert cake onto rack. (Don't wait too long or the cake will stick) Cool completely. Sift powdered sugar over cake just before serving; slice into 16 pieces.