<VV> carb balancing

[Paul Abel]

Hi All, In preparation for installing the secondaries on my 66 140 
engine,( PO was running just primaries) I am trying to get the primaries 
balanced better. Engine is basically running really well, but the LH 
carb is sucking way more air than the RH. I can stall the engine by 
covering the LH carb, but not the RH. Carbs were rebuilt 2 or 3 years 
ago. I've noticed that I can wiggle the throttle shaft on the LH carb, 
enough to alter the idle speed. I'm assuming I need to rebuild that 
shaft. I can also hear a slight vacuum leak at this spot.
1- Why is the carb with the leaking shaft the one which sucks more?
2- Will rebuilding that shaft make it easier to balance the carbs?

I also see a thin plastic tube coming off of the balance tube. The end 
is sealed with a piece of tape. This engine came out of a 66 Corsa, so 
I'm assuming that was the line for the vacuum guage, is this correct? Is 
this a possible source of a vacuum leak? Is there a better way to seal 
off this connection? I have a 65 500 coupe, so I have no guages (yet).

Thanks in advance for your replies.

Paul Abel
ACORNS / CORSA
Rochester NY