Preheat oven to 350 degrees F. Place papers in 24 muffin-tin cups. In a mixing bowl, beat eggs. Beat in mayonnaise. Mix well with devil's food cake mix, water, and vanilla. Divide the batter among the cups. Bake until toothpick inserted comes out clean, about 25 minutes. Cool. For the frosting, melt semisweet chocolate chips in a double boiler; whisk in sour cream. Frost the cupcakes immediately.