The '87-'90 YJs came with either a fuel-injected 2.5L inline-four or a carbed 258ci (4.2L) inline-six. Jeep's much-admired fuel-injected 4.0L six came online in the '91. Owners of carbed 258s can add complete EFI systems from companies such as Mopar Performance and Howell Engine Developments. The Mopar system shown here on Matt Winters' '90 258 is reportedly an easy bolt-on, including the intake manifold with injectors, a computer, sensors, an electric fuel pump, and a new distributor. And the gas tank does not have to be modified.