Reduce oven temperature to 350°F. In 2-quart saucepan, heat pineapple, sour cream, granulated sugar and flour over medium heat, stirring constantly, until boiling and thickened. Reduce heat to medium-low. In medium bowl, place egg yolks. Slowly stir 1 cup hot pineapple mixture into egg yolks. Stir this mixture back into remaining pineapple mixture in saucepan. Heat to boiling over medium heat, stirring constantly. Stir in rum extract. Pour hot filling into baked pie shell.