you need a 1:1 fpr. otherwise when you're at 8psi of boost your fuel rail pressure has been effectively LOWERED by 8psi (due to the pressure difference) and you will thus be getting less fuel. pressure is a relative measurement - normally taken in reference to atmospheric pressure (gauge pressure) rather than absolute pressure. if your fuel rail had a pressure of 40psi (gauge) and you were also boosting 40psi (gauge) then the effective pressure difference between the rail and intake manifold would be 0 psi. you would simply be dripping fuel into the mani.

-marc