Well, at level 100, it should have these stats, theoretically with perfect IV's.
341 HP
236 Atk
236 Def
259 SpA
212 SpD
236 Spe
It takes 108 Evs in Special Defence to get it back up to 236, thus getting rid of the nature stat drop.
Since i dont know your IV's, it takes a minimum of 108 EVs and a maximum of 232.
i would train it with 252 HP EVs, 252 Speed Evs, and 4 into SpD.