foam didnt help the surge on mine but if you want to try it i pushed cubes down the filler neck...
http://www.merlinmotorsport.co.uk/FUEL-SYSTEMS-Tank-Foam/c26_27/p737/56-CUBES-TANK-FOAM-(CUBIC-FOOT)/product_info.html

if not i have a 4l proalloy swirl pot i had made for my cos that is not of any use to me now(brand new).