what i have found with my os .40 fp (airbleed engine) is if you set the highspeed to rich (even a few clicks off) it wont transition very well if at all (engine dies)
so what i do is peak the rpm's then back off 4 clicks, and fly the plane for a few min, land, kill the engine and spit on the cylinder head, if the water instantly boils off i richen it a few clicks more. repeat until you find the sweet spot where the engine doesnt overheat and still transitions well. im sure theirs a better way to to that with a airbleed engine but it works for me.