Fuel injection systems operate at higher pressures than carbureted systems.  Many design types of electronic fuel injection vary widely in their operating pressures. Throttle body type injection (with injectors mounted above the throttle plates) operate in the range from 9 to 15 pounds per square inch. Port type injection systems (with injectors mounted in the intake manifold) operate in the range from 30 to 60 pounds per square inch.  Some newer direct injection systems (with injectors mounted directly into the cylinder) operate at pressures as high as 3000 pounds per square inch.  This extremely high pressure is needed because the fuel is injected into a high-pressure area