I have a 2004 Vectra diesel with the Z1.9DT engine. Had problem with chugging and smoke. Fault code indicated lamba so changed it, but problem still there.
Cleaned and then changed EGR but still not cured it.
Chugging has gotten worse and the smoke is too.
The idle is fine and starting also, the only other problem is small drops of fuel on floor each time I park up, under the engine.