Would a dump valve benefit my car performance wise, or is it just a different sound I will achieve, and if so, which one would you recommend? Thanks! Car is an 02 STi with PPP.

 

I have the same car

I removed an aftermarket one and fitted back a brand new original part, the noise was getting on my nerves and Subaru said it would make no diffrence to the performance and they were correct, we have a much better dump valve on our cars than the original design / prior shape scooby

 

If your car is running standard boost then there is no "performance reason" to change the existing recirc dump valve. If your car has been mapped to run higher than standard boost then there may be reliability problems with a standard recirc dump valve, in which case an aftermarket recirc valve should be fitted.

VTA (vent to atmosphere) dump valves give you a whoosh or whistle and no performance advantage. In fact they may give you a performance disadvantage as you are jettisoning metered air, meaning the mixture in the cylinders will be too rich for a short period after the air is vented.