My '68' parts book calls for a paper air filter element in the TR6R & C but cloth in the T120's. I'm wondering why. Which provides the best filtration? Which provided the best flow? Would engine longevity be improved for the T120R by switching to paper? The TR6C is a competition bike often rode in the dirt so the max filtration thing would be an issue but the TR6R and T120R are street bikes and use different elements.