Did some more research.
These carbs are Emissions DHLA40H type 5304P and 5305A, and were fitted as new to Alfetta 2.0 Berlina and Alfetta GTV. The original DHLA40E (non-emissions) which were fitted were replaced.
The standard jetting for these carbs on Alfetta was (mine in brackets):
Main 150 (150)
Main Emulsifier 7772.11 (7772.10)
Main air corrector 210 (210)
Idle 58 (58)
Idle Emulsifier 7842.3 (unknown)
Idle air corrector 220 (in the carb body, not the jet holder)
Pump 40 Horiz. (35 Vert)
Pump volume 8cc (20 strokes)
Float 7298.1 (7298.1) 8.5g
Float height 14.5-15mm (14.5)
The jetting for DHLA40G on a GTV2000 with emission carbs is the same, except Main 145, 7772.10, 35-40 depending on model, pump volume 9cc.
DHLA40G is supposed to be near identical to DHLA40H.
I checked the pump stroke, mine is set near minimum.
The jetting seems to make sense, particularly as I have an Alfetta distributor. It could be that the issue is with the accelerator pump not delivering enough fuel.
So, I am going to try resetting the pump to 9cc of fuel per 20 strokes, and consider enlarging the pump jet to 40, horizontal spray type, if that doesn't work.
I took this information from DHLA Dell'Orto perpetual leanout part II - Sideways-Technologies Forum
There are factory jetting tables there for these and many other models, as attached.