High Pressure Fuel Tank

1994 MR2 Turbo. On hot days especially, the pressure in the fuel tank builds up excessively. If I let the car sit in the garage, the vapors fill the garage and house with fuel smells for many hours. If I open the gas cap to vent the pressure (before pulling down to the garage), I can get vapors venting for 2-3 minutes with a significant flow. Otherwise, the car runs fine.

Is this likely a problem with the carbon canister not bleeding pressure somehow?