In a glass bowl or casserole dish, combine the lemon juice, soy sauce, ground ginger, and garlic powder. Place the pork into the dish, cover and refrigerate for several hours or overnight.
Heat the oil in a wok over medium-high heat. Add the pork, marinade and onion, and cook stirring constantly until the meat is cooked through. Throw in the carrot and broccoli, and cook for a few minutes, then add the peaches with the juice, and bring the mixture to a boil. Sprinkle the flour over the mixture, and stir in. Cook, stirring, until the sauce thickens. Serve over rice or noodles.