Marinade: Make the marinade by mixing together the barbecue sauce, garlic salt, black pepper, sugar, oil and cornflour. Pour over the pork chops, let sit for 15 minutes.
Sauce: Make the sauce by mixing together the tomato sauce, water, barbecue sauce, sugar and pineapple syrup. Set aside.
Stir Fry: Heat a large frying pan with oil over high heat. Pan fry the pork chops until brown on both sides; 3-5 minutes. Reduce the heat to medium and cook the pork chops until done; 3-5 minutes more. Set aside.
Heat the same frying pan with oil over high heat. Stir fry the onion with salt until soft; about 3-4 minutes.
Stir in the green capsicums and sauce then heat through; 2-3 minutes.
Stir in the pineapple and pork chops then mix well and serve.
Adjust the flavour of the sauce before cooking with it. If it's too sour, add sugar. If it's too sweet, add vinegar.