After selling the wrong model idf's i'm now looking at a more suitable pair.

If you are running a 1.7 with twin webers what is the carb set up that you have?

On the image below it looks like there are 5 vacuum take offs on the two carbs, can anyone shed any light on these?

Click to view attachment

Theres only one vacuum pick-up the others are used for balancing throats by Alfa mechanics,they only bleed off when open,you can run a vacuum dizzy of the upper port for a SVDA or 034.
Alfa Romeo only used one vacuum port on these carbs which gave enough signal for the distributor,some say yes some say no but it makes sense to me.
Only one carb will have a vacuum pickup as per Webers or Dellorto's used on the AR engines.
You have a 1.7 engine so keep the vent size smaller to suit,most likely 30mm or 32 if your motor is breathing better with a carb cam etc,if not stick with the 30mm and you will have good power down low....that's where u need it.
Check Alfa jetting set up carefully its not always correct for a T4 engine.

My 40's just have little threaded brass plugs in the (4) holes below the throttle plates. The carb on the right has the distributor vacuum port. Plug the rest.

I have a carb sync for a motorcycle with four hoses to four tubes of mercury. I was going to use the lower ports on mine to sync the carbs.

I've now ordered a different pair, set of 70's made in spain with 1 vac port on each and jetted to suit the t4 motor.