Put the turkey steaks on a plate; pour over the stir-fry sauce, turning the steaks to coat them all over. Cover with cling film and put in the fridge to marinate for 10 minutes.
Meanwhile, make the salsa. Put the chopped tomatoes, green pepper, pineapple, coriander and chilli in a small bowl. Add the lime juice and mix well. Set aside.
Heat the oil in a large frying pan and add the marinated turkey steaks. Cook over a medium-high heat for 2½ minutes each side, until cooked through with no pink remaining. Remove from the pan and keep warm.
Add the noodles to the pan along with the mange tout and remaining stir-fry sauce. Cook for 2 minutes, until heated through. Remove from the heat and stir in the chopped coriander. Divide the noodles between 4 plates and serve with a turkey steak and some salsa on the side.