Ever since mounting my Sporty tank on the backbone it's reduced the range I get out of the tank by about 3 litres.  Not so good for an 8 litre tank!

I got a bit lazy when I mounted the tank and didn't do the proper mods, ie rellocate fuel cap and petcock.  So I've bitten the bullet now and ordered all the parts I need to mod the tank i.e new fuel cap and bung which I will put right at the top; frisco petcock bung which can be welded to the back of the tank.  All good right.  See pics below of the fuel cap and petcock bung that I got.

My only issue is that I'll need to cut out the existing filler bung which has a pressure pipe going from the bottom of the tank to where the existing filler is. 

What do I do with the pipe?

I can seal it up from the bottom and just remove it but I suspect it's there for a reason.  Or should I redirect it and locate it under the new filler bung?