Does this just space out the intake manifold or does it change the shape of the plenum to smooth the flow into the ports? I know on the Fost the manifold and head don't mate up perfectly, causing a step/wall and subsequent turbulent flow.
Having the spacer smoothly transition between the two shapes can definitely improve things.
Is that what's happening here or is it literally just extending the shape of the intake manifold another 1cm or so without adapting to the head port size/shape?