In addition to three other suggestions I had earlier for balancing the stim. I want to suggest the idea of having an up period and down period. So when a player is stimmed they get an adrenaline boost, ok more movement speed and health as is, then there should be a equally long period after where they cannot reinject and are lethargic, that is equally slower and only perhaps 85 health max (but maybe being slow is enough). Then they have to use it when it counts and not be constantly on the juice.