I've recently read that Impreza Turbos have a BOV as standard. Is this true???

 

no all turbo imprezas have a recirculating valve that reciculates air back into the turbo inlet and doesnt vta

 

If one doesn't upgrade the boost settings, would the standard re-circulating valve be best left alone?

 

A recirc valve should do the job no probs - some of them were prone to leaking (makes a mooing sound) but forge do a replacement. If you want to get good whoosh there a re loads of valves but if you have a MAF this is know the cause the car to run rich. There are also Hybrid valves that vent both - to atmosphere and back into the system - APS, Forge, Turbosmart, GFB. Its the usual loads for and loads against. Down to you but SUBARU did spend alot on developing what youve already got - sometimes - if it aint broke - dont fix it!!