Clacking Freelander

Please Please some one help. I have a 53 plate Freelander TD4 that when you drive it at different speeds and at different revs, it can also occur when you rev it up stationary you get quite a loud clacking noise. This can make the vehicle omit black smoke and makes it feel like it is miss firing.

What I have had done to it so far:

New pump and pressure regulator.
Changed pressure regulator in case it was faulty
Replaced fuel filter
Replaced all air filters
Tried different injectors
Changed turbo boost valve
Had the wiring loom checked (as best as possible without removing it)
Changed oil and filter
Blocked EGR valve
Checked and changed some vacuum pipes

The only thing I haven't changed is ECU.

Any ideas would be much appreciated.

Interpretation of other peoples description of noises is difficult so that is why you may not have received any replies.
One thing that causes a lot of clattering noise which isn't often considered is the torsional vibration damper on the auxiliary drive pulley. The outer pulley is bonded to the hub through a rubber ring. The rubber cracks and lets the pulley flap about. Easy to see if you take off the flexible slash shield ibside of the front O/S wheel.

Vic , thanks for the reply but it is defenitly fuel related (electrical) some where. I actual went out in it two weeks ago and it drove great only "clacked" twice, someone else tried it the next day and it was as bad as ever. It can run fine and then it seems as if it starts to inject at the wrong time and black smoke comes out of the exhaust with a missfire jolt. If you drive it steady and keep lifting your foot up and down on the throttle it seem to ease the situation. Since I posted the first listing we have also tried changing the crank sensor. last things to try fuel pressure sensor onthe rail, ECU or ripping the engine wiring loom out!

I'm thinking: intermittent wiring fault- known culprits are connections to rail fuel pressure sensor and injector harness for which a replacement section may be available via LR. I would also check the connections to the throttle position sensor under the dash. I take it there are no stored fault codes?