Toyota Aurion 2007: Shake and rattle from engine

WE BOUGHT a Toyota Aurion ZR6 in July 2007 and think it's great, but it hasn't been without its problems. At the 1000km service we reported the engine had a flat spot when going from deceleration to acceleration, such as coming out of a corner. It also had a ticking sound characteristic of a cam/valve noise and an engine rattle somewhat characteristic of piston slap when cold. Both noises mitigate as the engine warms up. A letter to Toyota Australia head office did not even get an acknowledgment. The dealer response was fairly typical -- ``it never happened'' or ``it is found to be characteristic of the vehicle''. Does this mean all Aurions have this problem? I will continue to press Toyota on next service, but expect to have further difficulties because I have converted to dual-fuel LPG, of which they do not approve. Not good enough, Toyota.