Escort Cosworth's have what I'm told is a 'Purge Canister System' which looks to vent from a small pipe on the top of the fuel tank to what looks like a valve which leads to the front of the car (nearside inner wing) to another valve which has a pipe to the inlet manifold and a pipe to a caninster under the offside front arch.

What exactly is this for? I'm guessing its a way of drawing fuel vapours into the canister but why? to stop the fuel filler cap hissing when you remove it? or for an environmental reason?

The inlet manifold pipe has been blocked ever since I've owned the car so I doubt it works anyway and I was intending to remove all of it, is there any reason why I shouldn't?