RFL relieves compressor pressure surge caused by changing gears or backing off the throttle and has been used on turbo charged engines running upto 35 psi boost.
This valve is set up for a 2002-ON WRX OR STI. Its pretty much brand new. Has some scratchs on the top but works perfectly. Actual picture will be up shortly. This is what it looks like tho.
Thanks for looking. JIM