The hyperflow unit is a copy of the subaru spec C in tank anti surge system. If you keep your eye out on ebay you can normally pick one up for 150-200 which includes the whole fuel pump assembley, or if you are good at DIY sort of stuff you could make your own easy enough, im pretty sure Dave made one for his bug sti and put some pictures in his build thread somewhere.
http://www.perth-wrx.com/vb/your-dri...es-02-sti.html
Have a look here too see what the spec c unit looks like.
http://www.perth-wrx.com/vb/mechanic...-assembly.html
I wouldn't get to caught up on the fuel surge issue unless you want to be ultra competitive running less fuel for weight saving. As long as you keep the fuel topped up around 3/4 you will be fine.