Neat little video, but IMHO doesn't prove much. What you would ideally like to see is a small vacuum on the other ports to help scavenge the cylinders.
Inherently a couple of brand manifolds would fail both those tests and if I get around to making a thread on the manifolds I will try to explain why.
As far as the up pipes, we always make our manifold outlets slightly smaller diameter and the up pipes slightly larger. We have checked about 20 - 30 manifolds and they seem to be pretty consistent. That being said checking them with a gasket would be the best idea.
Inherently a couple of brand manifolds would fail both those tests and if I get around to making a thread on the manifolds I will try to explain why.
As far as the up pipes, we always make our manifold outlets slightly smaller diameter and the up pipes slightly larger. We have checked about 20 - 30 manifolds and they seem to be pretty consistent. That being said checking them with a gasket would be the best idea.