There's a Few good things,
Best first mod- Full service; New oil, oil filter, Fuel filter, Air filter,
Check the plugs are gapped properly- new ones maybe too.
Just give it a full overhaul on fluids- you don't know how long it was sitting in Japan,
Check all vacuum connections.-lines etc.
Then once it's got that;
Few things like the "Hose 10 mod", Silicone bends instead of the pipes to the turbo,
And I think it was either hose 1 or 2 from the bbod you put a restrictor pill in to remove VOD.
Also a strut brace and a K brace makes these cars handle like they're on rails.-If you've got good tyres.