carb spacers?

[pimperout]

im thinking about gettting a carb spacer and am wondering about the power it could add and what sounds they make, im looking at getting a 2 inch spacer my friend said it gives the gas more time to atomize so it burns better and the added air volume under the carb helps reduce back pressure or sumthing about when you let off the gas suddenly the thingers (my mind went blank for the proper name) that let the air in snap shut im not sure about what that would do but he said its best to have as little of that back pressure as possible or sumthing, and i have also heard they make kind of like a whisling or whiny sorta sound when you giver gas i dunno, mabe some 1 could clarify this for me thanks.