Starting problems after engine overhaul

Hi,
My 1.9 TDI AHH engine was completely overhauled about six months ago due to a major turbocharger failure. (The cylinders were honed, the cylinder head was reworked, new injectors were installed, the fuel pump was refurbished, etc.).
The engine is running perfectly again.
I've only been having problems since the start...
However, these issues only occur after prolonged periods of inactivity ( > 12 hours).
After starting, the engine runs roughly and shakes for about 1/2 minute. At the same time, a large cloud of blue smoke comes out from the back. These symptoms seem to worsen in cold weather.
After that, it calms down and runs normally and smoothly, and the smoke disappears.
It was suspected that there was air in the fuel line. The DiFi (likely referring to a specific component), its bracket, and the fuel line were replaced. But still the same problem!!
The beer lines were replaced with transparent ones. Sometimes, air bubbles form in those areas after prolonged periods of inactivity.
Is that normal? Could air be drawn in through the nozzles?
What other potential causes could there be for these startup problems?

Thank you very much for your tips!

titas

While the issue of air in the supply and return lines has been discussed many times before, here's a reminder: In addition to using transparent return lines, it's also helpful to use a transparent supply line from the filter to the pump. The valve located on the filter often leaks. Then, fuel may flow back into the lower tank, and during engine start, more air may be drawn in and then vented back through the pump.

Since the problem worsens during colder seasons, there's a good chance that there's also a defect with the glow plugs.