What does Power Boost do in the following cases?
You increase Radiation Infection's Defense and ToHit debuffs for ~15seconds minus RI's activation time.
You increase Radiation Infection's Defense and ToHit debuffs for ~15seconds.
You increase Fortitude's Defense and ToHit bonus for the full duration of the (Fortitude) buff.

Thanks. I'd include an exclamation point, only my keyboard is broken.
Heh. No worries eh?

As a general case answer:
1) Power Boost buffs the effectiveness of powers activated while Power Boost is active for the entire duration of the buffed power
2) Toggle and Auto powers function by constantly reactivating the toggle/auto power
2.a) Therefore, Power Boost affects toggle/auto powers for approximately the duration of Power boost (give or take a couple seconds, depending on exactly when in the activation cycle the toggle/auto was in and whether the toggle was activated after PB)
http://www.fimfiction.net/story/36641/My-Little-Exalt
Having Vengeance and Fallout slotted for recharge means never having to say you're sorry.
I hit power boost, then Radiation Infection
I hit power boost, while already running Radiation Infection
I hit Power Boost, then Fortitude