it is a piece that you attach to your stock T-body to smooth out the incoming air like the aftermarket ones.

 

It bolts right on the stock throttle body

http://cgi.ebay.com/ebaymotors/ws/eB...sPageName=WDVW

 

Is there any reliable evidence it does any good?

 

Nope, but i dont see how it could hurt. I have heard of there being problems with the little idle air thing (the little hole between the two butterflys on the bottom of the TB) being obstructed by the Air foil, like the foils hole not lining up right and this can affect performance.

 

Heres some as close to reliable as youlll get evidence that i know of
http://www.ws6.com/mod-4.htm

 

I guess that answers the question.