Your love of TLAs is killing me. What do you mean when you say CVS? It's not ringing any bells for me.
Vacuum in the tank? Sounds like someone either tried to delete the evap control system (the charcoal canister is part of it) and didn't have a clue or it's plugged up... either way it can result in cavitation of the fuel pump impeller.
EDIT: ROFL!!!! Bought it AT CVS.... the store... never even seen one but heard of them in the past... I feel like a tool.