Tuned port injection is a type of fuel injection system that combines newer technologies to utilize fuel economy and airflow to combustion chambers. Tuned port injection systems were designed as an alternative to the antiquated carburized systems.
Tuned port fuel injection took the place of "old style" carburetors in American muscle cars, beginning with GM cars in 1985. It is designed to deliver a more consistent and reliable air flow to combustion chambers, producing more bottom end power and increasing fuel economy. The pulsing air being drawn into the engine is moved along a tube runner and is delivered to the combustion chambers at just the right time. This air delivery system actually allows the air being ported to the combustion chambers to enter the chamber on its own; it does not need any help. This fact accounts for the increase in horsepower.
Tuned port injection fuel delivery systems offer a number of advantages over carburized systems, mainly in efficiency. They also offer an increased throttle response and, as mentioned, can produce more horsepower. Since their inclusion by GM, tuned port injection systems have gained in popularity and are being used in many more vehicles than they were in 1985.