Its to meet emissions controls.

I believe the following... Any fuel vapors from the tank pass threw the canister via a PCV valve and the carbon is meant to neutralize it before it enters that atmosphere...

Basically a pain in the ass... My ute has one too as its an 85, not sure when they were introduced.

EDIT: You can see the metal fuel line that comes from the firewall direction. Can anyone provide any info on the 'thing' that the other two lines go to? as I have dellortoes on and one is just looped back onto the other.

Carbon cannister is no pain. It simply prevent petrol fumes from going into the atmosphere.

The fuel tank is sealed. The only vent is a steel line coming up to the engine compartment to the Cannister.

The two hoses are "fresh air" and "purge vacuum".

For details, see Carbon Canister in our Tech wiki.

Some systems use a solenoid for purge what does the stock system use? I'd love to find one for my EFI conversion

The late ute uses a purge line stock

earlier aussie datsuns (e.g. B310) used the Flow Guide Valve which doesn't work as well and often goes bad

aussie B110 used no fume control, tank was vented into the owners garage cough, cough ...