1in large mixing bowl combine the melted margarine, eggs, sugar and extract. Blend well. Add flour, and milk alternately until completely blended. Add the baking powder, cinnamon, and salt. Fold in peaches last. Prepare muffin tins, with paper liners or cooking spray. Fill each section to about 1/2 full. Mix together: 2/3 c of brown sugar, 2/3c flour, chopped pecans,oleo and cinnamon, and sprinkle over each muffin. Bake for about 18 - to 20 mins...when the centers spring back. Cool in pans for about 5 mins, remove and cool completely on wire racks.. Yield about 3 dozen.