Ford Falcon 2004: Vibration

I BOUGHT a 2004 BA XR6 early last year. After three months I could feel vibration through the whole car and took it back to my Ford dealer, where I was told there was no vibration. But further tests showed a severe vibration. During the next six months they replaced tie-rods, fitted a new tail shaft, new diff, new wheels and tyres, but still could not find the vibration. They now say they don't know what to do and the matter is closed. The vibration is worse.