Throttle lag is virtually eliminated. Throttle lag is where the airflow in your carburetor out accelerates your fuel, which finally catches up. Modified or piped machines will have fuel needs that require a higher fuel curve when the pipes and modifications kick in. In other words you need one fuel curve when running below peak and another fuel curve at peak horsepower. This is why a piped machine is so fussy to jet.
More horsepower requires more fuel.
Spark plugs will last longer. The plug color will be lighter and piston wash will be minimal or disappear due to the improved fuel delivery and combustion efficiency. It's not a case of starting and stopping from one position to the next. There is a great deal of overlap with each setting. For the most part you will seldom need to adjust the dial.