Whisk together cornstarch, water and soy sauce in small bowl until blended; set aside.
Heat 1 tablespoon oil in large skillet or wok over medium-high heat. Add onion and pepper; cook and stir 2 minutes or until crisp-tender. Remove from skillet; set aside.
Place remaining 1 tablespoon oil in skillet. Add chicken; cook and stir 4 minutes or until no longer pink. Return vegetables to skillet. Stir in pineapple, bamboo shoots, sweet and sour sauce and soy sauce mixture; cook until hot and sauce thickens. Serve with chow mein noodles, if desired.