exhaust cut-out, y pipe flow

[tcodi]

I saw on "trucks" how stacey put electric exhaust cut-outs on copperhead. He used a Y-pipe after each header secondary to split the flow two ways. One path led to a cut-out, and the other through the muffled exhaust. I think this is cool as hell and would like to do it, but I'm wondering if the Y-pipe would affect flow and sound when the cut-out is closed. I've attached a .pdf sketch showing the exact layout.