replacement steering box

I just came from the alignment shop they set everything they could but said the steering box needed to be replaced as it keeps wanting to pull to the left. They had the car on the machine and showed me with the wheel centered and front end up on the jacks the tech reved the engine and the wheel moved by itself to the extreme left. His opinion was that some vale in the box was bad, The power steering pump is relatively new Boullchon Performance .Need help in which direction to go from here.