Mass Air Adjuster for 1986-1995 Mass Air equipped Mustangs. This will fit all vehicles with the oval 4-pin OBDI style mass air meter.Features a large adjustment range that is extremely easy to use. Provides you the ability to adjust the mass air voltage for engine modifications & injector changes. This helps to eliminate engine surges & driveability problems. The mass air voltage is a primary factory in your engines air / fuel ratio. Digital display shows the mass air sensor voltage.