slight misfire

[Tenstar]

Hi all,
connect 55 plate 1.8 tdci
poor starting but goes eventually !
ticks over fine no issues, but throttle it to 1800 -2000 rpm it feels like its misfiring shoves out a fair bit of smoke,
drive it and it feels under accelleration like its on 3 pots after 500 yards or so its fine, loads of power and drives real well
no codes at all
done a leak back test....pic attatched

fe55 leak back.jpg

any ideas???

thanks in advance