Blitz dump valves?
 

On ebay I've found brand new Blitz super sound dump valves which are less than half the price than they are over here (shipped in from Japan).

They say that they are universal fitting and will fit any car. I have a 2005 impreza uk300 and am thinking of buying one. Has anyone else bought one of these or can anyone advise whether they would be easy to fit or a total waste of money!!??