Thanks for the advice guys, i appreciate any input on this one.

I've reprogrammed them once in firing order (i.e. 1-3-4-2) and once in cylinder order (i.e. 1-2-3-4) and neither has helped. I also reprogrammed all 4 each time, using the codes from the injector bodies.

Each injector looks ok on the leak-off test and each is measured at 3ohms resistance.

I'm loathed to put a £400 injector in a car unless i'm confident that is the issue, but at the moment i'm not confident which, if any, are playing up..........