Well guys, a final update to this sordid story.
I did forget to mention that approx a month before the vehicle developed its first fault, I had a long range (140ltr) tank fitted by ARB in Hervey Bay. ( I also had Old Ma6n Emu suspention fitted with airbags).
Anyway it appears that the tank contained a large amount of welding slag/splatter and this clogged the pickup as well as this the fuel lines were routed across the top of the fuel tank and were partially crushed between the top of the tank and the bottom of the tub/tray thus starving the engine of fuel, especially on acceleration.
Ian Boetcher Motors of Ipswich, the dealership that sold me the vehicle, in conjunction with Nissan arranged for the vehicle to be transported to Ipswich and in less than two days had both diagnosed the fault and rectified it!
This cost me $1688.00, which I paid without hesitation.
This cost will, of course, be presented to ARB in Hervey Bay.
Ian Boettcher Motors also supplied a loan vehicle for the days that they had my vehicle.
The loan vehicle was a 2013 Navara ST with 19 kms on the clock. This is not the first time that Boettchers have assisted me. Is it any wonder that I have bought a number of vehicles from them and, although they may not be aware of it, so have a number of my friends.
For those of you that posted suggestions, please be assured, they were all considered and I learnt a lot, Thank you for the support, all of you.
I am not leaving the forum and will, from time to time contribute where I can, again, thanks.
PS The 550 is an awesome tow tug, I was getting worried that it may have had some inherent problem . . . . . it hasn't !!!