In a large skillet over medium heat, brown meat in oil; drain. Add onions and garlic; cook and stir 2 minutes. Add the enchilada sauce, tomatoes, chilies, salt and pepper; bring to a boil. Reduce heat; cover and simmer until meat is tender, about 2 hours. , Combine flour and water; add to beef mixture, stirring constantly. Bring to a boil; cook and stir until thickened, about 1 minute. , Warm tortillas; spoon 1/2 cup filling, off center, on each one. Fold sides and bottom of tortilla over filling, then roll up. Spoon a little more filling over top of burritos. Serve immediately. If desired, garnish with tomatoes, olives, cheese, sour cream, onions, lettuce and guacamole.