This is the ventilation valve assembly: ToyoDIY.com
There's two ventilation hoses. One goes from the right side of the rocker cover to the open side of the throttle body. The other goes from the back of the rocker cover to the vacuum side of the throttle body by way of the PCV valve.
It won't be the valve that's clogged. It's only open under vacuum anywayz and isn't mean to equalise crankcase pressure. It'll be the other one that is more likely the problem. Part number is 12261-74020. That being said, it could actually be both. There's lots of oil vapour in there when the car is running and over time it can clog things up.
Basically what's happening is your engine is generating vacuum, as it should, which opens the PCV valve and sucks blow-by back in from the crankcase. This is probably working fine or you would have bigger problems (bad idle, lean surge, etc). When you turn the car off, the manifold pressure becomes higher than the crankcase pressure so the valve shuts. The second hose (without the valve) is there to equalise the pressure. If it's clogged, that will never happen and you will have a bit of negative pressure in the crankcase. So, when you opened the crankcase you increased the air pressure and what you heard was the air rushing back in.
So, just take off both hoses, check and clean. Also check and clean the manifold inlets to make sure everything is open and happy. Should be a simple fix. Take you 5 minutes.