After extended research on the subject it appears this would be a good mod on the NA cars.., and not the turbo cars apparently.
Invariably it appears the dual exhaust would disturb the backpressure, and possibly exhaust flow needed by the turbo. In addition it appears a highly tuned ECU would be needed to take advantage of it.
So decided the single 3 inch exhaust using a aeroturbine resonator and muffler will be my preferred method of addressing the increased exhaust flow needed for the next performance level I'm looking for.
to be continued...