In a small mixing bowl, combine brown sugar, soy sauce, vinegar cornstarch, and water. Blend thoroughly and set aside.
Sift flour over both sides of pork medallions.
Coat a nonstick skillet with low-calorie cooking spray. Add 1 tbsp oil and heat for 1 minute of med-high heat. Add pork and saute for 3 minutes. Turn and cook 2-3 minutes longer. Remove pork from skillet and set aside.
Add remaining 2 tsp oil to skillet. Add green peppers, onion, and carrot. Stir-fry 4 minutes, or until vegetables are tender but still crisp. Stir in soy sauce mixture and pineapple tidbits with liquid. Bring to a boil and cook 1-2 minutes longer, or until sauce is thickened.