Manifolds are not the simple devices they once were.
Most cars have active (read - variable) manifolds these days to squeeze
the last ounce of performance out of the engine. Varying the intake
runner length according to engine speed is one way they do it and they
have various ways of achieving this. This site will explain;
https://www.samarins.com/glossary/intake_manifold.html
--
Xeno
Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)