it improves air flow and provides cooler air to the engine than a stock airbox. both of these things would give small performance gains. however, the zed has a helpful ecu than cancels out any gains from this mod also the zed's stock airbox is very good anyway, and some induction kits could actually work less well than stock . . .
they do sound awesome though and really improve the look of the engine bay. i've got a pipercross and its great.