Just noticed that when my 03 WRX PPP is at idle and I turn the steering wheel i can feel a tugging sensation. If I increase the rpm slightly the sensation disappears. The steering has only just started to act like this and I'm not sure if it needs to be looked at during it's 20000 mile service? Any advice please.

 

check the power steering fluid

 

At the risk of sounding like an idiot, have you checked your front tyre pressures? - I recently had very similar symptoms to those you've mentioned and it turned out I had a nail in the driver side front tyre - tyre pressure was down to 12PSI replaced tyre, set pressure to 32 - no more tug