To be entirely clear, it's not a full "400R" body kit. The body kit is: the 400R front bumper, without the front air ducts (this already exists in-game); a refitted version of the GT-R rear wing; and the standard Autech GT-R rest of the body (side skirts and fenders, with a regular sedan rear bumper).
Also, I repeat, the "ER33" is just the GTS version. The GT-R sedan gets a BCNR33 chassis code just like the coupe.
Ooh, nice - that's a good, solid picture of the 400R coupe rear diffuser, though. Thanks for that!