I have a new to me, since October of last year, 1987 Toyota MR2 with the C52 5spd, with about 111k on the clock.
In October I drained a really old, black stew of gear oil from the C52, and filled back up with Redline MT90 - I was surprised to find the drain plug didn't have a magnet. Last weekend 3\9 - I drained the MT90 (Treating the first fill as a flush over that first six months) and refilled with Fresh MT90 and MOS2 for gears - plus a magnetic drain plug.
I can't tell any real appreciable difference, except for one that reverse is consistently easier to get into. The gearbox shifted much better after the first drain and fill, the second which was really spurred on more about installing a magnetic drain plug to catch any metal debris - continues to shift fantastic.
MOS2 hasn't had any appreciable issues with syncros since the refill. If anything of substance happens in terms of grinding or issues that show up, i'll post about it.