Automotive

Electronic Fuel Injection.

EFI may refer to:

[edit] Computing and technology

• Electronic fuel injection, an internal combustion engine technology
• Extensible Firmware Interface, a Firmware interface specification

[edit] Organizations and institutions

• Enrico Fermi Institute, a research centre by the University of Chicago
• Equestrian Federation of Ireland, an equestrian sporting body
• European Forest Institute, a research centre
• Expeditionary Forces Institute, the overseas branch of the British NAAFI
• European Friends of Israel, a political organization
• Evangelical Friends International, a Christian religious organization

Since you posted it in the Automotive Section, it probably refers to Electronic Fuel Injection.

Good one Bruce, that just about covers the bases, however, you did miss EFI according to Wellington (Perishers- Maurice Dodd); "Electronic Fool Injection".