Is it the JTD?
If so I've had loads of Alfas' with the diesel engine, still have in fact.
The 20v 5 pot used to be a sod for throwing a wobbly, 10v was much more tolerant.
Usually it was the EGR valve getting gummed up. They can be stripped and cleaned rather than replaced.
If not then the MAF gets dusty/dirty so can be cleaned.
MAP sensor sometimes, but I'd lay my bet on the EGR,
It should be the 16pin OBD2 plug which if the same as Alfa systems is within the fuse board under the steering column.
If it's teh petrol version though, I don't know