I think you'd be fine with the IWG, as rotaries do not tolerate high exhaust backpressure at all since they're almost like a 2 cycle in many respects.
That said, a well placed EWG is superior for boost control - no doubt about it. A crappy EWG placement is going to make your life difficult no matter how large the valve.
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S13 Hatch - Goes around tracks quickly
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