As i said on the previous page, we're working together with the dev to resolve the problems that have appeared since the final build of the game launched. In the beta build things were performing normally, but now that's not the case. I don't know why that is, or what has changed, but we're working on it.
They worked closer with nVidia that's what happened lol. Some where along the lines it's messed with the AMD optimisation most likely.