Wow thank you Ian for answering the asked question, all i can add to it is wasted gas is energy that has been used to do work.
Ian i think john has made the venturi so the turbine gases is low pressure and wategate pressure is high therefore this will extract gases from the turbine to make the turbo more efficient under boost i can ask him again, i understand where your coming form also.
100% agree on how you have explained the turbo selection as john said he wants ie 20% exhaust gas to drive the turbo to desired boost the rest waste. I guess the theory is all here just need to see it all happen.
Also i am in the process in installing all the Pressure and Temp sensors again another huge task as sensor placement has to be done all correctly as any data has to follow a trend and not give false reading due to incorrect placement, this will be all done with Johns guidance.