Renault Laguna variable power assisted steering on laguna mk 3 2010 2.0ltr 150 dynamique.

Having many problems with the Variable Power Assisted Steering on Laguna Mk 3 2010 2.0Ltr 150 Dynamique. Noticed that the steering appeared to be getting easier/lighter when speeding up instead of stiffening firstly totally opposite to what usually happens and occasionally car seemed to wonder slightly taking a shallow corner or bend under speed. Firstly tried checking fluid level in reservoir which I found hiding under N/S front wing which was a little low so was topped up after checking that no ingress of dirt had got into reservoir. This was to no avail so my local garage suggested taking all the Pump/Motor off and taking it to a power steering specialist a couple of units away from him. When we took it to them they couldn't test it even with the vast amount of test equipment on hand as some of the connections couldn't even be connected to with weird configurations etc. Pump was refitted, etc and tried again but still no difference. All the steering components,springs,ball joints ,track rods & anti-roll bar etc have been checked along with the tracking 3 times and all found to be sound. The conclusion was that the Pump/Motor was probably at fault/failing so a new one had to be found eventually coming from Paris as there wasn't one in the whole of the UK. This has now been fitted and at extra cost been coded to the car|||||||||||||||||||||||||||||. The steering is now a lot better but I am still left with the slight wondering on occasions and two tyres have had to be replaced at the front as they were showing signs of wear on the inner inch or so and only 4 months old from new and the tracking has been redone yet again which was only very slightly out. Any suggestions would be appreciated as the costs are now starting to mount up on the heavy side. Regards