I run the breather hose almost the same as you - a small filter and tucked in behind the rear cylinder. It certainly seems to be coming from the breather filter, so I'll pop the bolt on the tappet screen tomorrow and have a look (if it will even come off as its been a good 10 year sine I checked it)
I'll also have a good look around the heads as well to make sure its not there.
Its made a bloody mess of my new pipes!..lol sigh.
Here is a snap from after today's ride:
Gosh i really really love the look of the 2:2 units!