In this episode they are discussing the various intake manifolds for the early G3, and how the MP single plane is the absolute worst of the choices.
Their combo made under 400hp with some non-M1 dual plane.

Yet, Richard Holdener made over 440hp with that horrible M1 single plane on one of his tests on an early G3.

I’m thinking the early G3 sample used for this test was particularly weak, and isn’t an accurate representation of what would be a typical result.