I'm aching for a Karting like setup with a removable section that can be replaced. In kart racing 2 strokes does it this way so you can turn the engine for higher or lower ranges depending on the track. You have a section that fits on the end of the header, the pipe fits on the end of the changeable section. It's all head together with some very tight springs. Then you could tune it. Later easily make it longer if you went to ride someplace with hills for example.