RE: os 91 fs tends to die after 20-30sec idling
Mine did exactly the same thing. I had to lean out the low speed needle quite a bit (1.5-2 full turns, if I recall) to get it to idle reliably. Make sure you don't lean it too much, though, or the engine will die when you transition from idle.
I don't have a bunch of experience here, but from what I've read, you lean the low speed needle until the engine acts like it's going to die when transitioning to full throttle. Then richen it until it transitions smoothly. Worked for me, anyway.
I'm still breaking the engine in, but my idle is around 2600-2800 with a 14x8 for as long as I want.
Chris