Combine steak sauce, wine, lime juice, garlic, chili powder and sugar in 13 x 9-inch baking dish. Add flank steak, turning to coat with marinade. Cover; refrigerate 4 hours or overnight. Remove flank steak from marinade. Stir cornstarch into remaining marinade until smooth; set aside.
Heat oil in large skillet over medium-high heat. Add green pepper and onion; cook for 2 to 3 minutes, stirring constantly. Remove from skillet. Add flank steak; cook for 5 minutes, stirring constantly. Add vegetables and marinade; heat to boiling. Boil for 1 minute, stirring constantly. Serve with tortillas and sour cream.
Servings: 6