your bottleneck for efficiency is always at the manifolds and then where the Y hits the single cat. If you can open that up, that's where it will make the biggest difference. Whether you go 3" or duals after the single cat, really only is a visual and slightly different sound.
It has true duals on it now and has been on for almost 5 years now. I would go From the 2 cats into the single 3" back from there. I don't need to do anything, but if I could gain something I might try it.
Thanks
