Yep - GM have been playing with this idea for ages. The 24v version of the old Senator B had two ports which opened at different engine speeds. They needed it to get the old (circa 1960s) I6 which was already struggling to make 160hp with FI up to 200 without losing any low end torque.
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Originally Posted by Wikipedia about the Opel Senator
The main feature of the new engine was a "Dual Ram" system, increasing torque at low engine speeds by means of a redirected air flow system engaged at 4,000 rpm.
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Is it similar to the idea of twin choke carbs - a smaller port at lower speeds with less fuel and then a wider one ? All the old cars I muck about with have SUs
According to this
Variable length intake manifold - Wikipedia, the free encyclopedia
Toyota's version of the variable intake manifold is this
T-VIS - Wikipedia, the free encyclopedia
which looks to have been replaced by VVT in the early 1990s. But it looks like it makes the same basic advantages. Looks like quite a few people have tried it too.