Shuddering when driving at normal speeds

I have a 2009 C4 Grand Picasso 1.6hdi auto, it has developed a quite bad shudder when driving at normal speeds, I have been to a citroen dealer and was told it was the clutch so I had a new clutch and dual mass flywheel fitted, it seemed better at first but now it is worse than ever, I have cleaned the EGR valve and dont know what to do next, the shuddering sometimes happens when the car is stationary with the engine running, I have discovered that when the shuddering start, if I pull over, put the car in manual, floor the throttle and take off there will come a cloud of black smoke from the car and afterwards it will go great for awhile, maybe weeks, there are no warning lights coming on although the anti pollution warning light did come on sometimes and also danger of DPF becomong blocked warning, driving at high revs in a low gear seems to have fixed these, can anyone help? Please