[mwebb]

so
first off
i see some of the systems in images here in this thread are tightly woven
messes

flow in them is going to be UN consistent at best
and that is exactly what is NOT wanted


dynos are useless for measuring flow
imho

this simple waveform capture shows exhaust pressure per cylinder (green) with intake pressure (red) with secondary spark which roughly shows about 10 degrees before TDC of each cylinder
note
how UN even and erratic the green exhaust pressure / flow is

on a stock G10 Geo Metro with the engine not running , just operating the starter , that is because of the way the exhaust manifold is configured .

at higher rpm under load
exhaust flow is
tragic
but
it will be no WORSE than what the "alleged " header systems depicted will show
compare to this


there is a long line misfire to the left of center but
excepting that
look at the blue trace , note how uniform each exhaust pulse is
at cruise around 40 to 45 mph
that is what is desired a uniform pulse train
you will never achieve a uniform pulse train with a knotted pretzel shaped exhaust
you will never see this using a dyno or hypothetical software

does this matter
yes it does
turbulence is never your friend when you are attempting to improve VE

and that is your goal to IMPROVE VE
you can not improve VE by reducing VE .