Grease and flour a 10 inch fluted tube pan. In a large bowl, combine the cake mix, sour cream, oil, water, eggs, pudding mix, liqueur, orange peel, and cinnamon. Beat with an electric mixer on low speed until blended, scraping sides constantly. Beat on medium speed for 4 minutes. Add chocolate chips. Pour into prepared pan. Bake in a 350~F. oven for 50-60 minutes or until tested done. Cool on wire rack. Dust with confectioners' sugar if desired.