If you make your own velocity stack how should the inlet be situated? Cut at an angle and facing into the airstream, or the angle shielding the inlet from the airstream? Or, should it be cut off at 90-degrees. It seems to me that you would get a pitot effect that would actually suck instead of force mixture down the throat with a 90-degree cut. Does a trumpet shape actually do anything?

I have notticed that piston ported engines spit a little mixture back out. I don't see any cure to that, other than a reed valve design. Would a really long velocity stack, or intake manifold, do any good on the spitting fuel issue or are there consequences that would negate the thoereitical gain in effeciency?