mondeo 02 reg dura torqu 2.0lt tddi smokes alot on start?

hi there
i have a mondeo 02 tddi i just had the engine changed
o cold start the engine smokes alot and makes knocking noise's
the smoke is a light colour with tint of blue.
once the engine is warm its fine and runing smooth, no smoke but a slight kocking noise on excelleration still remains.
i have shown to loads of different experts and they are all giving me different views.
can you please help me.