The engine behavior is not dependent on the type of carb, only the rich/lean mixture. Air bleed carbs can be VERY sensitive to small adjustments. Starting with the hole 1/2 blocked is usually a good place to start.

What fuel and prop are you using? I have a GP-61 using a 13x4 APC, and it turns at 13,000 RPM and idles well around 2750 with Omega 15.

To check your idle mixture, start the engine, then at full throttle, adjust the high speed valve to peak RPM less 300-500 rpm to the rich side. Now reduce throttle to your lowest reliable idle. Let the engine idle for about 30 seconds, then punch the throttle to full. If the engine hesitates, then goes to full throttle, the low speed mixture is rich. If it goes to full throttle without hesitation, your done. If it just dies, your low end is lean. An alternative check is to pinch the fuel line. If there is a slight rise in RPM when you pinch it, your rich. If it dies immediately your lean. If it continues to run for a few seconds without RPM rising, your close. Use both tests.

Now based on your results, you can make a small adjustment in your low end needle. Remember with an airbleed carb, turning the screw out will LEAN the mixture, and vice versa. Make your adjustments in 1/8 turn increments. Then you MUST reset the high speed needle as before and repeat.

Take your time. It might take a few tries to get it dialed in, but once you get it, you'll never have to mess with it again.

Good Luck.

Brad