Anyone who experienced big puffs of white smoke from exhaust when startup, but only sometimes, like every second, third or fourth time. I have switched engine oil but there is no difference, the coolant level is fine.
The engine runs rough on low speed sometimes, if i stop the car, swith it off then restart it, it runs like a champ again. Can it be leaking injectors?

it could simply be water vapor condensed in cold exhaust. Or could be coolant. Have someone stand near exhaust and smell for coolant. If the white smoke does not persist after startup I wouldn't worry.

It happens sometimes when the engine is hot too, so i dont believe it could be condensation, and it doesnt smell coolant or burnt oil aswell, the levels are fine, i think that it could be some injector that leaks, because the sound from the engine is different just after startup, then when it stops smoking from the exhaust it sounds and runs as it should.

Probably just condensation in the exhaust - it happens naturally inside the pipes (after the engine, no worries)

do a compression test