Well i have an update to this.
Recently i've used liqui moly diesel purge, I've had a terraclean done on the engine and I've just replaced the injector loom with a brand new one.
Just been for a test drive, loom seems to have made a difference to pick up and smoothness but the injector balance has remained roughly the same.
0.02,-0.61,-0.89,1.46
I had a look for cam wear while i had the cam cover off and by the looks of things the cam is all shiny and no signs of scrapes/scratches, so thats good news.
Am i right in thinking now that this must be injector 4 needs replacing/balancing?
Many Thanks,
S10EAT