88 Mustangs did not come with mass air. Mass air started in 89. If you currently do not have a mass air conversion on your 88 Mustang you do not need to add a mass air conversion to use this kit. You have a speed density car with a map sensor not a bap sensor.
Yes you do if the mustang is speed density it's a one setting only it will not adapt to any cam,head or Intake work you would need to convert to mass air flow if not equipped . Only california 1988 mustangs 5.0 were equiped with mass airflow all others states started in 1989.