Help II - 2.4d DW engine - Noise when revving

[blix99]

Hello.

This engine is really testing my resolve.
It's in a 1983 VW LT camper. I've had it about 2 months.
Trailered it onto my drive after buying it and there it's sat ever since : (

Anyway. It had fuel problems (air in the lines and a leaking injector pump seal) which I fixed. Then the timing was out so I fixed that
All good.
I decided to change the glow plugs as part of general servicing. Took a while as the IP and vacuum pump were in the way and I didn't want to remove them if i could help it but I managed.

I then found some new injector cores (needles and nozzles) which I've just fitted. However, I now have a worrying sound going on.
I've just read this thread and it might be the same issue (hopefully nothing more sinister) but I'll post my vid anyway.
If it just just something with the injectors, this will be a relief.

https://drive.google.com/open?id=1vu...zm3lBF5aPUOwtg

It starts and idles OK but doesn't sound smooth or 100% on all cylinders. It smokes a bit too.
I've cracked open the pipe on the top of each injector in turn and the engine is affected by all 6 (the revs noticeably drop for all)
As you can hear from the vid, it revs OK most of the time but will then make an awful knocking noise. I'm worried about valves, cam, crank.
However, during my previous fixes on this engine, as mentioned above, it didn't seem to do this at any point before rebuilding the injectors but the sound seems pretty drastic.

Any help / ideas / advice gratefully received.
Based on the other thread I linked to, I think I'll take out all of the injectors again and just recheck everything.