Looking at MK2.5 Sport-any better than other special eds?

The Fuji diff is still a Torsen type diff, but Torsen is a copyrighted brand name. The Tochigi Fuji Super just uses extra cone clutch's to add a little preload, and it is the weakest diff in the MX5 lineup.

Mazda weren't fitting better diffs to the later cars, they were cost cutting by fitting poorer quality TorSen's

The fuji uses a standard 75w90 oil gear.

We have kinda drifed from the OP's original topic here, hope nobody minds.

No the Fuji is still just a Torsen type diff and requires only a standard oil gear.

Type1 Torsens are the strongest but they lock quite harshly, great if you like going sideways not so great if you like going round a racetrack fast. The type2 Torsen is still very strong, in fact I find it hard to see any MX5 breaking any Torsen type diff (our turbo'd MX5 race car runs a Type2 and produces over 375ft/lb's of torque, its been fine for two seasons), the type2 diff locks much more progressively IMHO its the diff to use for any serious track car.

Sorry what I mean is it should be a standard GL5 oil for the diff, NOT GL5-LSD oil.

Stick with GL4 for the gearbox though, the fives speeds were designed to use GL4 80w90 (GL5 can rot the brass syncro's). The six speed uses GL5, BUT our experiance shows that its a little too slippy for the synrco's and can cause crunching again I would stick to a GL4 75w90 even in the six speed.