mpfi change over

i know this is a lame question but what is the purpose of the mpfi??

it utilizes one fuel injector per cylinder instead of just having 2 in the DX, it provides more horsepower, and is required on all engine swaps.

thanks where is the best place i can buy one so i can swap

i only know of 3 places: ebay, someone selling theirs, or the junkyard.....and quite possibly a combination of all 3

How much of a HP gain can be expected from MPFI? 5 or 10?

about 8-10 should be expected.