Cook macaroni according to package directions; drain.
Meanwhile, lightly saute shrimp in oil; remove shrimp and set aside.
Drain pineapple and add 1/2 cup of the syrup to skillet with vinegar, brown sugar, salt and soy sauce.
Bring to a boil; mix cornstarch with water and add to skillet.
Cook, stirring constantly, until clear and thickened.
Add green pepper; cook and stir until green pepper is almost tender.
Stir in macaroni, shrimp and drained pineapple; heat to serving temperature.