dump pipe

:bandit: I have all the good stuff in my exhaust system,3 and 4" stainless but standard dump pipe.What sort of power increase would I get from an aftermarket one and how much dollars and where from in qld

ok, i got one atm i'm selling to fit a r33 gtst made by specially custom exhaust with the oxygen sensor moved right away from the turbine gas exit. selling for $300