Port Fuel Injection (PFI) is a method used in internal combustion engines to deliver fuel to the engine's combustion chamber. In this system, fuel is injected into the intake manifold, where it mixes with air before entering the cylinders. This process helps improve fuel atomization and combustion efficiency, leading to better engine performance and reduced emissions. PFI systems are commonly found in many gasoline engines, including those in cars and trucks. They offer advantages such as smoother operation and improved throttle response compared to older systems. However, they may be less efficient than direct injection systems under certain conditions.