10 seconds is a long time. I don't think I have anything that I could run in a straight line away from me for 10 seconds at WOT and comfortably see
the one thing that OS has been known for over the years is the easy tuneability......... wide needle settings. As they have tried to go for higher performance that feature has gone away somewhat. The 21 RG is very needle friendly. If it's not a user tuning induced problem then there is something wrong with the engine. One thing to remember, if you are going to be running WOT all the time, set the needles slightly rich. Don't go for that thin edge, your engine will thank you for it.
Ed M.