The picture they have where everything is blocked out except the car and the diffuser is PS-ed. Look at the tip of the left muffler... it gets cut off from the image of the diffuser..
how do you know raceon made a replica of the RE amemiya one? and how do you know that its been wind tunnel tested?
Look at RE Amemiya's rear diffusers for the FD and then compare that to what ROUSA made. The style is basically the same not to mention they announced in a zilvia thread that they would be attempting to modify a RE Amemiya's to fit the 240sx and add it to their production.
RE Amemiya is famous as one of the most prestigeou aftermarket companies in Japan. They use the same FD rear diffuser on their JGTC FD's and they have been known to wind tunnel test their diffusers and some of their FD's bodykits.
btw here are some pics too compare the ROUSA to the styles of RE Amemiya's rear diffusers. You tell me if race on came up with that diffuser on their own.