Its very hard to compare stages between individual car makes and companies. One company's stage 2 might be another company's stage 4.

Its really just a useless measure with the lower numbers meaning more streetable and the higher stages more race applicable stuff. I laugh when I hear people say that they're running a stage 3 turbo, stage 4 clutch. I'd just rather hear GT30R turbo, Exedy twin-disk clutch.