thanks for the response.
Unfortunately the car was manufactured in 2006 and hence is out of warranty (it has been purchased by me 3 months ago)
Regarding the manifold I was told by the official dealership that it has broken flaps and that it is most probably the reason for preventing regen to take place.
Unfortunately in Cyprus there are not many garages which are dealing with Alfa Romeo and the only logical explanation regarding the problems that I have with the car has come from the official dealership. (others told me that it may be a failure of one of the high pressure fuel injectors, which has sounded to me a bit exaggerated)
The problem is that I cannot find the manifold in Cyprus, not even a used one, and hence I was considering of using the vauxhaul one, which I was told that it is the same one as that of Alfa 159. (ordering a new one will cost more that EUR 850, it will take time to arrive and there is no guarantee that will resolve the problems)
Will the complete removal of the dpf as you suggest resolve the problems I have, irrespective of the replacement of the inlet manifold?