I think a lot of people don't know what they are talking about here..
The Athena Racing and Stage6 Racing are NOT the same.
And the Stage6 is not a yet a well know cylinder here in the netherlands. Some people who are replying here haven't seen the cylinders for themselves.. so some reply only 'what they heard'.
I would go for the C16 untuned.
But tuned.. what do you called 'tuned'?