crossram

I remember reading about these in a book called "Scientific design of exhaust and intake systems". There was allso a small graph showing how this manifold significantly increased torque around the midrange over a conventional intake.
The graph didn't really show any specific values, but the intake was used as an example of real life application of the "tuned length" intake principle. According to the book, it was never to successfull in mass manufactured applications due to the practical problems related to its size and warm up/ fuel distribution issues.

But from a performance point of view, there is nothing going against this design as far as I can see.

In a way, the Magnum "beer keg" intake is a variation on the same theme, but here the runners are curled up, something you can do with a "dry" EFI intake where fuel distribution and drop-out is not an issue.

In short, from a performance and engineering point of view, this intake is cool.
From a manufacturing, maintenance, and mass market point of view, it is un-cool, which is why it's not more common.