Brad might be able to get into his “way back machine” and find some results from a stock vs modified M1 single plane test.
I don’t recall how modified the non-stock one was though.
I would say I don't want the intake to be the restriction compared to the heads.
It would generally depend on how you tested it, to establish how much of a restriction is there.
Any time I’ve put a cast single plane manifold on a head and tested it on the flow bench, the flow goes down.
If you tested the intake on its own, it could very well flow a higher number than the head by itself.
