4 into 2 onto 1 exhaust header

["Michael Salter" <michaelsalter@rogers.com>]

I need to design and build an exhaust header for AHX12 (100S engine) to use
in the upcoming Aussie / US Challenge series. 
I have been able to find a formula for a 4 into 1 system but cannot find a
formula for a 4 into 2 into 1 system which reputedly produces a wider power
band. 
Can anyone out there help with this?

Michael Salter
www.precisionsportscar.com