[T2] hole in throttle plate

[Jack Dinan]

On my 35 PDSIT dual carbs, I have to advance the idle speed screws 
until they are almost at the end of their travel before I notice any 
change in the rpm at idle.

I just noticed that a hole had been drilled in the throttle plates. 
Could this hole be the cause of the insensitivity to ISS position?

My theory goes something like this. The air that flows through this 
hole is enough to satisfy the requirements at idle. When the ISS is 
originally set to give a gap of .005 between edge of the plate and 
the carb wall, the air flow in this gap is so much less than the flow 
through the hole that the effect of opening or closing the gap is 
small.