LOL Well Alex pointed out that Yamaha was done it
If I were to invest that much time and energy into making something like that, I'm sorry to say it probably wouldn't be with the 250
My favorite runner idea was in the early 90's ZR1 Corvettes. They had 2 intake runners per cylinder. One of the intake runners had a butterfly on it which only opened up at like 3,000 RPM. So you would literally go from a long runner intake design at low RPM's to a huge tunnel-ram type manifold at higher RPM's...
... One difference though is it was a TPI fuel injection set-up, so the intake runners were dry.