The problem with Speed Density is, that by changing many engine components you will adversly effect the volumetric efficiency. Speed density can detect some changes with it’s MAP, TPS and ACT sensors. It can not detect that you have changed the volume of air coming in and out of the engine. A Mass Air sensor directly reads the mass of air (number of air molecules). By doing this, it can detect the changes in the volume of air, in addition to it’s pressure and temperature. This metering process allows the computer to adequately adjust for increased airflow resulting from the addition of throttle body, upper/lower intake, cylinder heads or camshaft. Converting from Speed Denstiy to Mass Air will allow your engine to reach its full potential and is an integral part of any performance build up. Fits the following vehicles.

1986-88 Cougar

1986-91 Crown Victoria

1988-91 Grand Marquis

1986-92 Mark VII

1986-1993 Mustang (5.0L)

1986-88 Thunderbird (5.0L)

1988-91 Town Car