I have seen a lot of differences in the N21-5T series that I would almost think that it is made out of left over parts but the 5 porter sleeve with M.E.S. is not used in any other engine so it must be a production. The funny thing is that all engines are almost the same on the track, the one must be set to rpm and the other with a different gearing to the torque.
Today it seems there is a more stability in the production, all engines of the last months so far I have seen have the same timings which is almost in the range of the old NovaMega EVO5 / RB C5 models.