>>34439328If you go first after the boost, you go first after the boost. If you are worried about speed tiers, just remember that the speed orb that was mentioned takes the spot of an item, so it would only be used on Pokemon that don't use a specific item. Landorus would have a max speed of 401.7, but let us assume that stats always round down, so 401. It would outspeed any of its threats, but it wouldn't be able to beat them all.
