Hey Cameron,
Just a few quickies before you drive yourself nuts with the Dellorto Dilemma. Without telling you to suck eggs, make sure that the ignition system isn't breaking down at the higher revs- you may have a voltage drop that indicates the motor leaning out (not enough fuel), but it is in fact, not burning the mix thoroughly. Do all the normal checks for coil, spark plug(s) and leads and ensure that there is no drop through them as well. Check for air leaks around the inlet side of things too...
Through experience I can say that providing more and more fuel to a problem that doesn't require it, ends in tears...