How do I know if i have speed density or Mass Air
 

I have a 88 mustang but I'm not sure if i have speed or mass air. The guy that owned it before me did some stuff to the car but I'm not sure if he converted and I don't know what either system looks like. How can I tell? thanks

This is how I tell:

Look at the air inlet tube from the fender opening to the throttle body. Is there a small box with wires from it?
If there is then it's mass air. If not then it's not.
Unless it's a California car, which would have mass air installed at the factory.

What he said........If there isnt a mass air sensor on the air inlet tube then it isnt mass air.