I'm thinking of putting the old MAF back in. This is what showed up the failing loom/ injector. I'm assuming the new MAF s increased signal is increasing the fuel demand and causing the week component to become evident. It all started very quickly, just after I filled with budget fuel without my normal additive.

I have been working away at getting my TD4 running properly.
Surprisingly the MAP sensor was causing mine to miss and stutter each time I changed gear.
Its the small insignificant sensor on the left hand side of the intake manifold.
Simple cleaned it with brake cleaner and she is now smooth as silk.

FOR NOW, its a land rover after all.

I cleaned the MAP sensor when I cleaned the gunk out of the manifold. As I'm getting a variable MAP signal, I'm guessing it's ok. I'm thinking along with Mike that the injector harness is breaking down or an injector is on the way out.