Can only boost Psychic monsters, and only for that turn.
These monster help you search Power Injector from your deck. Of the two, Serene Psychic Witch is more preferable since she special summons Power Injector from the deck. But Doctor Cranium can also be used to add Power Injector to your hand by paying 800 LP when he is destroyed by battle.
Here are some support cards for your Psychic deck. Since Psychic monsters use a lot of LP as cost, Brain Research Lab can be used as an alternative cost. Psi-Station boosts your monsters even further, while Psychokinesis gets rid of monsters on the field. Psychic Overload recycles your graveyard and nets you card advantage.