I am not trying to discourage you, just trying to help you think things through so you don't run into any unexpected problems.
So the 2nd TB is going to be dependant on boost pressure, but what actually opens and closes it? Now that I think about it more, a simple flapper valve installed in a reverse Y might do the same thing and need no other mechanicals. Whichever side is flowing more is going to push the valve open more.
I can see quite a few pitfalls to this system and it will obviously not make the power it would without it on, because of all the restriction that will be added by valves, the extra turbo (with TINY exhaust side) and such. You would probably be better off to just go with a centrifigal supercharger or a 50 trim
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