Ok, someone pick apart this concept:
In the interests of aiding a weak exhaust port to the maximum possible extent, how 'bout putting the cone or 'megaphone' right at the exhaust flange, ala a 2-stroke style header?
Wouldn't the cone then positively affect the sound waves that push out from the port immediately, thus helping scavenging?
Two-strokes have a reverse cone further down the tube, past the expansion chamber that supposedly sends back a weaker, differently timed wave to help with keeping the intake charge from squeaking past the exhaust port, but if you don't build in that feature, wouldn't the concept help a normal 4-stroke port too?
Or would the benefits be outweighed by a normal tube-header design?