I've been running FS for some time too. But maybe it's worth buying a bottle of SS just to confirm your theory.
I was using SS a few years back but I wasn't really tuning my bikes much back then, so who knows, I might be missing something now. One thing I do not like about SS is that it eventually clogs up the exhaust. I know for sure my bike's much cleaner now days on FS.
Also, I had a friends 2002 Rev3 live at my place for a year or so. When it came emission and oil control I found that bike's engine to be dirty and disgusting, regardless of what oil or petrol we used ...even after we fitted a new muffler. And I've seen many Beta's that behave the same way since. That's just my experience but I could be wrong.
Best of balance.
Neo