Thanks guys.
Found more info at www.steedspeed.com
BENEFITS:
1, Easy installation in even the tightest location2, Superior flow due to large port area around entire circumference of the charge air pipe.
3, Excellent sealing against boost pressure leakage because boosted air can’t apply pressure to the valve to force it open, unlike other designs which require adjustment for higher boost levels.
The valve consists of a pipe which is slip fitted and sealed to the charge air pipes using high quality O-rings. This pipe is perforated with a ring of ports which are alternately covered or uncovered by means of a ring shaped piston which wraps around the pipe and is actuated by vacuum and boost pressure to open as soon as the throttle is closed.