Many dealers, and even other shops, start by telling the customer they need a new throttle actuator. This gives them a sort expectations budget to start from, i.e. weeds out the people who don't want to spend any money. It's sort of a worst case prognostication, and it's ususally wrong. Faulty throttle actuator is terribly overdiagnosed and very unlikely the problem in your case given the recent replacement, which is all a long way of saying get a new shop.