The 5.8 L, 351W, was changed during the '90s from speed density to MAF; performance gains were directly affected. Before 1994, the 5.8 L was equipped with speed density. This programmed coding was placed into the vehicle's computer to tell the motor how much air it should be getting, therefore supplying an appropriate amount of fuel. However, if modifications are made to increase air flow, the computer does not provide more fuel until the oxygen sensors register a lean burn and only then can the computer compensate fuel trim. After 1994, the engine was changed to mass air flow (MAF). This allowed the computer to directly read how much air the engine was receiving through the help of a sensor in the air intake as long as that exact sensor was used (MAF sensors cannot be upgraded for increased flow without using an aftermarket chip, reflash, or ECU. The rest of the intake system can be modified in any number of ways, but generally the MAF sensor remains stock). Because the computer reads this, it is able to increase the amount of fuel the engine gets when the air flow is increased, thus increasing performance.