I really liked the look of my existing GSD3s, but they don't come in 205/50/15 and I *really* needed some extra traction at the back. Further reading indicated that MR2s respond well to block-tread tyres, and longitudinal treads like the GSD3s exacerbate the MR2's tendency to tramline due to the MR2s lack of power steering.

Sounds about right. The MR2's lost a lot of the wrenching twitchiness and steamrolls over bumps where it would have used to be yanked off course. Mind you, having soft new rubber probably helps.