maybe this graph will influence ur choice
http://haveblue.org/dyno/5jun04dyno.jpg
winners:
aka 2 liter
evil detonator
sp maxflow (inline was tested, the manifold is almost as good and the vertical is probably not one of the top 5 or 10)
macdev gladiator
aka sidewinder
cp and the dye hyper 2 werent tested but the cp is supposedly not as good as the sidewinder