Hi I'm another MC18 owner that had the same symptoms
I used to need to swap the plugs over quite regulary 'cause they kept oiling up at low revs.
Mine needed a top end rebuild, an airbox cover mod (and a new set of ignition pickups from Lings Honda helped as well.)
... and if you've tried to derestict it make sure you disconnect the correct cable (Thanks again Wayne, it's still flying!)