Why does a chevy 305 tpi run like its lean and bad mileage?

A Chevy 305 TPI may run lean and exhibit poor mileage due to several factors, including vacuum leaks, a malfunctioning mass air flow (MAF) sensor, or faulty fuel injectors that fail to deliver the proper amount of fuel. Additionally, issues with the fuel pump or fuel pressure regulator can affect fuel delivery, leading to a lean condition. Clogged air filters or exhaust restrictions can also contribute to suboptimal performance. Diagnosing these issues typically requires checking fuel and air systems for proper operation.