i have an emenage blue in Cats daily S13, 850cc injectors, T518Z, cooler and exhaust. It works fine but with the 850cc injectors gets a bit borderline and i will upgrad it to the ultimate very soon.
i supose it come down to how far you want to go mod wise, if your not doing much more than you have now then go right ahead the blue willl be a great upgrade (plug and play box set is avail for R33) but if your planning on more mods down the track definately go the ultimate or PFC.