I would advise you to ditch the lot and install a Weber for your customer. This will eliminate all of the vac issues, make it a lot easier to tune and set up and is a huge improvement in performance over the original Mikuni carb (both power and economy) It will require an electric fuel pump to supply the Weber and trial and error to tune the ignition. In all honesty, the Aisin carb is a headache (not in the same league as the Mikuni but not much better)