Fuel coming out of breather pipe

[rangerstuart]

I had a replacement fuel tank fitted on my jeep , all well and good until I went to fill up and when nearly full, fuel started coming out of the fuel breather pipe.
I noticed that they had run x2 breather pipes from the top of the fuel tank down the side of the tank, which is where the fuel was coming out of.
Anyone else had a similar problem? and know best way to rectify?
I thought perhaps blocking off one of the breather pipes incase its acting like a vacuum when tank is nearly full and drawing in air through one pipe and pushing fuel out through the other. Or should I run the breather pipe up beside the filler neck ?
Any tips or suggestions gratefully received.

cheers

stu