Blow-Thru set ups.

aight, so what exaclty are the advantages of a blow thru set up...actually what exactly is it? i know it removes the MAS but what is the advantage of this? what from this site http://www.dejontool.com/3S.htm would i need to run a proper blow thru set up? do you need to reach a certain level of mods, ect to need a blow thru or is it just a mod you can do and get gains? i heard that i can run open BOVs better with a blow thru? thanks guys