Got some dyno results!
Still not tuned for the cutout, but with it open I picked up 46whp
over it closed with the stock exhaust! Also, notice how far the curve is moved to the left.
Solid lines are cutout open, dotted lines are with it closed.
BTW, I know my numbers are way low. This was a crazy-low reading Mustang dyno, as a GT30 powered 07 STI only put down ~330whp/318wtq.