I've used MT-90 (I may actually be using it right now..) as well, but also with the Shockproof-mix. I couldn't really tell the difference between the two mixes, but then my tranny has 200k on it and the 2nd gear issue. A new tranny is in the planning, but it'll be the crappy, J-Spec unit with shorter gearing.
I've also heard good things about the Royal Purple, but have yet to try it. Is it sold locally?
I've also heard good things about the Royal Purple, but have yet to try it. Is it sold locally?