The steering box was replaced as it knocked loudly if you rocked the steering wheel in the centre position, also if you put half a turn on the steering wheel there was about 2 inches if play before the wheels moved at all. The noises and whine have started since I got the car back. At first the steering felt awful (due to air bubbles the dealer told me) this has got better now and all I have left is this whine at low revs (when the engine is idling is when the whine is worst, it is still apparent if I increase the revs slightly too).

Could this still be due to residual air in the system and if so, how long should I expect it to last before all the air is removed ?

I am new to the crossfire, so where is the power steering reservoir for me to check ?