Heat oven to 350°F. Grease 13x9-inch pan. In small saucepan, cook caramels and milk over low heat until caramels are melted and smooth, stirring frequently.
In medium saucepan, melt butter over low heat. Remove from heat. Stir in sugar, vanilla and eggs. Stir in flour, cocoa and salt until well blended. Stir in 1 1/2 cups of the chocolate chunks and 1 cup of the pecans. Spoon and spread batter in pan.
Gently and evenly drizzle caramel filling over batter to prevent large pockets of caramel and to prevent caramel from reaching bottom of bars. (Caramel can cover entire surface of batter.)
Bake 35 to 40 minutes or until set.
In small saucepan, melt remaining 1/2 cup chocolate chunks with oil over low heat, stirring until smooth. Drizzle over warm brownies. Sprinkle with remaining 1/2 cup pecans; press in lightly. Cool 20 minutes. Refrigerate 1 hour 30 minutes or until chocolate is set. Cut into squares. If refrigerated longer, let stand at room temperature for 20 minutes before serving.