Like said above its a Boost a pump. The purpose behind it is that it will boost the voltage to the fuel pumps there for making them push out more fuel. It is so that when you have reached the stock limits of the pumps it is not needed to drop the tank and replace the pumps but rather install the BAP. This is needed in most cases in these cars when going over 500rwhp.
danny...yes it would be wise to add one...with just a 2.80 pulley and a 50 shot (non ported) i maxed out the fuel at 560rwhp...i would get yourslef some sort of MAF too...