Never existed, pretty much. It was a prototype that was abandoned due to mass engine failures. [edit: Well there's a few blurbs saying it went into production, but it wouldn't have been very many produced]
Using MW injection assumes you can run engines at full power anyways, and in 1945 the Japanese engine quality was in the toilets, so to speak.
EDIT: I think better options would be to wish for A6M5c and/or if you really want to wish, the A6M7, which was superior if I recall.
