Oversteer on right hand bends
 

My 99 Impreza turbo has started oversteering intermittently on right hand bends only. This happens across the speed range i.e even when not pushing the car near its limit. There is a slight whine from the rear. Could it be the diff ? I have replaced the rear shocks and the "C" shaped plastic bush/link on the rear but to no avail. I have driven the car for seven years so I dont think my driving style has changed.
Its going to catch me out sooner or later so I would like to get it sorted. Any ideas ? Thank you

I would say that it's more likely to be a wheel geomerty problem. The geomerty is not symetrical, so the car handles differently turning left than right. ;)

I will get the geometry checked, does this have to be done at a main dealer ? Thank you for the advice.

check its not powersteering related i remember a pump prob on a mates classic afew years ago may be wrong but sounds familiar

No, anywhere with laser alignment equiptment will do. They will have the data on the correct values.

First things first, check the tyre pressures and condition if you haven't already. ;)

I have had different tyres fitted and checked the pressure, so I think the laser alignment is a good start, thank you