Red, impressive results.
3:1:2 layout will only help at the top end I think, and only as a result of having an expanding area tailpipe. same thing can be done lighter with a single tailpipe.
Talk to your pipe man about trying a Cosworth style venturi at the tailpipe side of the 3:1 junction. I've used them a lot and they work to broaden the power band. I suspect they act as an amplifier/sharpener for the wave action. Experience with them says ID around 90% of tailpipe area and around an 8 degree taper on the outlet side.