Harold Johnson, Spitfire headers,Whats his Number?
agreed!
and I went from 340 manifolds to spitfires, and while I never dyno'd it I went from 13.3 @102 to 12.80 @ 108 swapping to them - thats not 16 hp
online calculators put that at over 30 hp - and they were 340 manifolds.
It weighs 3430 if you want to calc it out yourself.
http://www.wallaceracing.com/hpcalculatorquarter.php