Omega B Y25DT – Smooths very strongly white, worse in cold.

Hello, my Omega 2,5DTI (150 ps) smokes from time to time in cold condition, but not at the start. The qalm is white and really dense. It doesn’t need water, but more oil. I re-made before 3000km cylinder head after damage to the flaps. Oh, since the days is so cold the qalmen became worse. Thanks in advance for your help!!!