This being the case, then yes, even my gigantic exhaust housing offers a restriction to exhaust flow. That is evidenced by the exhaust back pressure readings I've taken.I think that was a fly-by by Lazaris.
I'm going to assume that Lazaris is saying that the area of a 1.5" valve multiplied by 6 would need to be the size of the inlet and outlet of the turbine housing, not considering the turbine wheel, inorder for the turbine housing not to become a restriction in the exhaust flow side of the engine.