X5 2001 4.4 sluggish starting when hot, no error codes

[SuomiX]

A long story short.
The motor died during driving. I changed a new fuel filter with a regulator, a new right side fuel pump and a new o-ring to the left side pump.
After that the motor started, when cold, quite normally. It maybe take a little longer time to start than before. BUT when the engine is hot it's a different game. If engine is started within 1-2 minutes again, it starts normally. If the motor is started after a longer time, the engine fires up very sluggish. The starter works normally and battery is at good condition. After the engine has fired up, it runs normally and fuel consumption, by onboard computer, is a little smaller than before. So the engine seems to work and no error codes is shown. I have INPA for error codes and diagnostic. The roughness page in INPA does not show big differences between the cylinders, they all are at the same level.
So what to do? Whats wrong? Coils, spark plugs(1,5 years old NGK), injectors...???