Ummm, I thought OS engine are ABN not ABC. I followed their instructions and my FX runs fine. The Irvine, however, is ABC and needs to get up to temperature quickly. This is pointed out in their instructions.
OS owners are lucky and spoilt. In most cases, their engines run well right out of the box with virtually no tweeking needed. I compared the instruction manuals for their LA and FX engines and found that in the LA book they go into great detail about how to set the low end. In the FX book, this section was missing! I know the FX has a needle instead of the air bleed but there is no equivalent section on adjusting it. The engine diagram doesn't even tell you where the low end needle is!

I think Irvine owners are just more knowledgable about engines. This partly shows in that you have to go to some effort just to aquire one. My Irvine needed a fair amount of tweeking of the low end needle to run just right but I'm not complaining becauase its a quality motor....