im pretty sure its the 7cm^2 housing on the turbo.

i like this kit, minus the fact it doesnt come with a BOV or FMIC but those are easy add ons, and the Emanage gives alot of room for improvement...drop in some 50lb injectors, Z32 MAFs turn up the boost and see where it takes you. definately not as cost effective as a hacked mafs setup or a chipped ecu, but the quality is there.

ive seen non-fmic'ed greddy kits for $2800, add on the $800 for the fmic and ur at ~$3600.