The tiny hole is the place where the vacuum created by the engine goes through to act on the diaphragm, raising the needle. Open the hole up, and when the butterfly valve opens, the drop in the pressure on the intake side of the carb goes down, sucking the diaphragm, raising the needle. This is the whole idea of a cv (constant velocity) carb. Open the hole too much, and the needle flies up too quick and kills the engine when you rev. It will not make the engine run ritcher or use more gas, but it will give you more response (which may make you more throttle happy, which may make your mileage go down). Find the balance that suits you. I drilled my carb a little, and it is more peppy.