in theory it would use the vacuum in the efi pipe to pull the fumes from the cam cover through to the can and then to the efi pipe. any heavy deposits (oil) would stay in the can itself. its probably the best way to use it i would say. keeps the oil out of the inlet.
I tried ot run it back in mate but got blue smoking issues when I did it. My can didn't have a breather set-up on it. So I disconnected it on the return pipe and cut it short and added a breather to it and it stopped the smoke problem... Was the only way my can would work.