that really depends on what its made of. What its designed to do is reduce the heat transfer between the intake manifold and the throttle body, those are made of a wood or wood/resin material. They also tend to lengthen the amount of volume in the intake mainfold to make your torque come on a little eariler. I think its BDL that makes an alumium one that is susposed to twirl the air or something, and although I cant say if it works or not, its not worth the $90 to try it out.
You can see the wooden ones on V8 fords and chevy's for those people that want to squeeze that last bit of HP out of their motors.
Andrew