Ray good to see that you have now come to some sort of a conclusion .
Yep, at least it is "some sort" of a conclusion.
I think I can find a 14T CS sprocket from an early Dr650 over here that will let me see what happens with the more "correct" gearing.
For now, it's very rideable and I quite like the "overdrive" It gives the bike a very different feel from the 750 engine but will still wheelie off the throttle in 1st gear.
Rob, I like you idea of punching holes next to the snorkle and will try this on an older air filter I have. It may just be the best of both worlds approach.
Thanks for all you comments (including livestock references that have now been added to my vocabulary).