P1472 VIS power/butterfly valves always open

I have a problem with my 2002 2.5 V6 Auto GS Freelander. It has a loud rattle noise that comes from the manifold. It sounds like it is coming from the butterfly valves in the inlet manifold on the right side. The gear changes seem a bit lumpy at times and it seems to lack power. The noise is worse when the engine is cold. I took it to a local garage and they hooked it up to their computer and it showed the error P1472 VIS power/butterfly valves always open. But they did not know what this fault was or how to rectify it. Can anyone help me out help me out and point me in the right direction.

Thanks
Lee
:fighting2: