Gareth - the tyres replaced were on our 2003 A6 Allroad (Pirelli). 2012 Allroad also has Pirelli, but the steering is horrid; nothing to do with wear I fancy, she runs and breaks straight and true. I am convinced by Google that it is an Audi malaise.
One quote - You could get your tracking checked...Also, perhaps look at the whole suspension geometry to ensure it's all as it should be...Also, check your tyre pressures...Failing that, welcome to the world of ill handling Audis!
And another - That’s in part because the car’s steering, although pacey, precise and variously weighty, lacks dependable feedback – even when Dynamic mode is selected – and fails to give a meaningful sense of connection to the front wheels.
Audis are supposed to be a little vague on road placement, aren’t they?
Written by someone else: In truth, there’s not a whole lot of difference between Auto and Dynamic, although we prefer the slightly more positive feeling of the steering in this mode. That’s because it always feels a little vague. If there was more of a build-up of resistance in corners, your confidence in the car’s directional stability would increase. And hard acceleration on undulating roads can uncover what feels very like a whiff of torque steer, despite all-wheel drive.
and so on ...