TD4 Problems

Hi i have a freelander TD4 2004 that has been having problems for a while and i am just wondering if anyone can help me. When i start it it turns over for a while before it actually starts and then when it does start if puffs out loads of white smoke. This has been going on for a while at first i was told it was my fuel pump which is over the back wheel. This was changed and everything was ok for a few days then it started again. I have been to many garages and had many things replaced....4 new fuel pumps (the one over the back wheel) a new turbo, 4 new injectors, 4 new glow plugs, the high pressure fuel pump in the engine, lots of sensors, filters and re wiring. starter motor, one garage even changed the clutch?? can anyone help me with this.