4-2-1 or "Tri Y" headers are good for low end torque and give up just a little on the top end. I've built headers for drag race cars for years and am building 4-2 crossovers for CB750s right now. I plan on a race version of a 4-1 as well as a turbo manifold, Tri Y would be a good addition to my line of pipes.
I'm not far from you (Brighton) so if you want to hook up maybe we can work out the details and build some headers.
Pics of the stuff I build on FB, search Sprocketwerx Motorsports.
Sprocket