In a large bowl, combine cake mix, eggs, sour cream, 1 cup coffee liqueur, and vegetable oil. Using an electric mixer, beat at low speed to blend. Increase speed, and beat 3 to 5 minutes. Stir in the chocolate chips. Pour batter into greased and floured 10 inch Bundt pan.
Bake at 350 degrees F (175 degrees C) for 55 to 60 minutes, or until tester inserted in center comes out clean. Cool cake in pan on rack for 30 minutes. Remove from pan, and cool completely.
Microwave frosting 15 to 25 seconds, just until soft. Stir with spoon, and add 1 1/2 tablespoons coffee liqueur. Stir well. Drizzle frosting over cooled cake.