Preheat oven to 350 degrees F. In a large bowl, combine cake mix, pudding mix, eggs, oil, sour cream, and 1/2 cup water. Beat with an electric mixer on low speed just until blended. Beat on medium speed 4 minutes, scraping down sides of bowl often. Stir in chocolate chips. Turn into a well-greased 12-cup bundt pan. Bake 50-60 mintues, or until a cake tester inserted in center comes out clean. Let cool 10-15 minutes in pan, then invert to unmold onto a rack or serving plate and let cool completely. Sift powdered sugar over top. Variation: Mocha Orange Chocolate Cake Before beating, add 1/4 cup coffee-flavored liqueur and 2 tablespoons grated orange zest to cake mix along with other ingredients. Proceed as directed in recipe above. Variation: Mocha Orange Chocolate Cake Before beating, add 1/4 cup raspberry-flavored liqueur to cake mix along with other ingredients. After adding chips to batter, gently mix in 1/2 cup raspberry jam. Proceed as directed in recipe above.