the only thing i know about this set up is that is very good to obtain the desired boost...without spinking like the single solenoid...that is why in big mod engine you see this set up..but i heard that when you install it you can verify a difference of bost when you switch it to off...my friend on his subaru has one and the set up is for 1.2bar...Meanwhile the hks is off the boost is under the stock boost...
For me the best controller i used was the Blitz with dual solenoid ...