What is this?

[dom14]

the charcoal canister is what the fuel tank breathes through, the rough idea is that the charcoal will absorb the vapours from the tank and its also plumbed into your intake allowing the vapours to be burnt when the engine is running. its an emmisions thing

if you remove the canister you will see a little tube sticking out that goes down into that cover you were asking about

Yeah mate. Now I understand. I obviously need to read more about these things in the Patrol manual.
I asked a pro mechanic few years ago and he didn't know and told me not to worry about it. Then I started getting into fixing the car myself when one day he couldn't help me due to being busy at that time. Ever since, I've been fixing most of the stuff and learning something new every single day.
It has saved my life couple of occasions. Nothing's more important than knowing the stuff about your car when you go for long trips.
Thanx mate.