I have fixed the 3rd piston problem by cleaning the fuse box connections & replacing the fuse (I think it was number 4 fuse giving the prob? but cleaned all the green off them all!)
I have removed the partical filter but left the cat in, then put an 'old school' in line fuel filter in the hose at the rear of the partical filter, with the intention to fool the difference sensor. The additive side was previously programed out & I have since removed a fuel cap magnet & fixed it to the sensor for it.
So far I have done about 150 miles with no probs but will keep you all updated, hopefully with good news?
Thanks for the help