The cai differences in performance are minumum. It does clean up the bay though. The stocker is a cia. However it is restrictive from the air silencer to the corrugated type rubber pipe. Also some companies make a kit and call it a cai when in fact it isn't. If it doesn't draw air from the fender it isn't a cai. Also the ones that put the filter on the end of a tube and leave it open in the engine bay are, imo, crap (you don't want to draw hot turbulant air).