Rowlie

I have a 2003 Nissan Patrol, ST GUIII 5 speed Manual, Diesel Turbo 3.0L with 310,000kms and all of a sudden there was a shimmie/shudder/vibration through the steering wheel. I checked tyres and yes due for a change so bought 4 new All Terrain TOYO's. Included was balance and wheel alignment. Same issue remained. It usually happens at 40 kph, 60 kph and 80 kph, but not always. I took it to a steering and suspension specialist and initially they tried by just replacing Leading Arm Bushes, The Front Body Mount - Bushing Kit Bumper, and the Superpro Panhard bar bush. No improvement. They then replaced the Steering Damper, Front and Rear Shock Absorbers. If just rolling along not under great amount of power it seems OK with no shudder, however under power it does seem to be worse - SOMETIMES. Don't no where to go from there. Have heard of others with similar issue and were unable to rectify. The vehicle is otherwise near perfect, so would like to keep it. Any help appreciated.