One thing that goes unchecked is the track rod and track rod ends, or possibly a worn wheel bearing. I had a similar issue on my old SR, replaced all the suspension, bottom ball joints, had new tyres fitted, balancing done etc. All work completed I still had same issue, so started to investigate further until I found that one of the track rods was worn causing the wheel to have a small amount of play equating to the vibrating issue. Hope this helps D