Hi chaps, after some help / advice with this machine.

Symptoms - this engine starts ok & after 30 seconds runs continuously rough at idle - in the same way as if the EGR Valve was sticking open.
If left running for 20 mins or so, it smooths out somewhat but never gets to a satisfactory, smooth tickover.
The correction values in MVB 13 have gone to extremes on cylinder 1 & to some degree on 4 when the tickover is at it's best.
It suffers, bucking / multi cylinder misfire at idle, but smooths out & runs fine at higher revs.

Tests so far;

Scanned fault memories - no DTC's logged

New DMF & clutch fitted due to clanking at idle / clutch judder & misfire. Not clanking, juddering any more since new DMF & Clutch - but still has rough idle.

Fuel pressure at idle - low pressure = 0.5 bar (scoped & looks good) high pressure = 3.5 bar at idle, over 10 bar when revved or return line clamped.

Diesel looks & smells of diesel - not black, fuel filter inspected & changed

Coolant temp sender scoped - no glitches from CTS.

MAF scoped - 2V at idle, 4.5V at WOT.

Injectors scoped - look the same as a good BKD we had in today.

Head harness inspected, looks okay, all 4x injectors give a reading of 0.2 ohms when resistance tested via pins in the head multiplug.

Smooth running correction values; when running as good as it ever runs at idle, (MVB 13)

Cyl.1 minus 3.1 mg/h
Cyl.2 0.68
Cyl.3 0.94
Cyl.4 1.34

Smooth running correction when idle is as rough as it gets

Cyl.1 minus 1.15 mg/h
Cyl.2 0.26
Cyl.3 0.26
Cyl.4 0.61

Injectors removed & switched 1 >3 & 4 > 2, no difference to smooth running correction, i.e still compensating heavily on No.1 & 4

Carried out relative compression test via scope, - highest peak 307A, lowest peak 304A.
Reflashed engine ECU to latest software version - no change.
Removed EGR & ran engine without it due to the similarity of symptoms to a stuck EGR - no change

No previous history on this car, new to us & to customer.

Getting a touch flummoxed with it at the moment,
any ideas?

The only saving grace is Frank Massey is having the same trouble with one in Aftermarket magazine.