Vladi

Mitsu's been working on it on and off for quite some time, I don't think they ever had enough cash or effort to make it production ready. I'm not hundred percent sure but from what I've heard they had problems with high temperatures which they couldn't solve or just didn't care to solve.
Nissan have always had close ties with Mitsubishi and usually when Mitsu comes up with something Nissan was most of the time the next one in the line to adopt it. If this is Mitsubishis technology that Nissan took over to develop for their own sake then it must have happened way before bailout, or it could be a case that Nissan just did all of this by themselves in collaboration with Renault. But from the drawings I see it looks almost identical to what Mitsu had in mind long time ago. Who knows.

situman

Not all modern engines are high stressed units with a giant-ish turbo strapped to it.