My initial thought was that you've got (another) split boost pipe, but they generally throw the engine management light on.
Hmm... I go for worn injectors, although a fuel filter costs almost nothing to replace, takes 5 minutes if you take your time, and will rule this out.
Mine was always a little smokey (not bad, mind) but this got slightly worse after the remap. Then it got a lot worse & the car dropped into safe mode... but this was just where the boost hose split where I'd installed a take-off for my boost gauge
One fix later, and it was back to "normal". I installed a K&N filter (nothing fancy, just the filter) and started using Forte stuff straight away (now on my 3rd consecutive fill of additive). I must say that unless I try to pull away in 3rd at 1000rpm, I now have almost no smoke.
How's your idle speed? Steady & consistent & not hunting? It's unusual for all the injectors to be shot - one dodgy one will cause the idle speed to "hunt" a little, and it'll produce the smoke you're experiencing.
The other think that'll do it is timing. When was your cambelt changed, and could the timing be a tooth out on the cam? The cambelt only needs to be timed on the cam & the crank - the diesel pump is just a pressure pump, so isn't timed as such. Could this be the issue?
Lastly (from me) disconnect the MAF (air flow meter, between the air filter housing & the turbo) & see if it makes a difference.
Good luck - keep us posted.