Well we thought we had it nailed when we came accross this



We took my t3 rose joint panhard rod off my car and put it on his, it felt a lot better in the rear (a lot more solid) but there is still a vague feeling when turning at speed.
Now the feeling definitely doesn't feel isolated to the rear, if anything now it feels like the steering isn't direct enough (even a slight delay while turning).
Back to the drawing board, but it looks like my mate is out of matsuri. Now we have a lot more time to fix it.