mass air conversion

87pony said:
it turns your speed density car into one that has a mass air....the computer is replaced with a different one but not eliminated

This is correct, on a stock car it has almost no affect on performance (if you use an large aftermarket maf housing), but it allows more extensive modifications to be able to be done to the cars engine than you can with an sd system without sacrificing drivability.

As he said it does not eliminate the computer, but it does upgrade it to a better, more complex one.