Guys, this is NOT A TWO NEEDLE CARB. As jester says, it is an air bleed carb. It doesn't have two interacting needles. Changing the air bleed adjustment has no effect on the top end needle adjustment because once the barrel opens the air bleed is closed off.

And his engine is not dying at high speed, it is dying on idle. It's good to hold the nose of the plane up to adjust the needle, but it's not going to solve his problem.

With air bleed carbs you don't necessarily get a minute of idle and then a great transition unless you've really got the right plug. With air bleed carbs, there often isn't much you can do with tuning to cure an idle problem because once the air bleed is all the way open, that's all you've got, and often the crankcase is STILL getting some fuel build up. Then you just have to have a glow plug that will stay lit when a slug of fuel hits it. The OS FPs work pretty well with the hole wide open if you have a good plug.

Jim