The mix screw is threaded into the carb body but it's covered over by an aluminum plug that stops you from getting at it. That plug is what has to be removed. You drill a small hole into it, thread a suitable sheet metal screw into it, and pull the plug out.
I actually carefully drill all the way through the plug. Take care to stop AS SOON AS you break through the plug. If you keep going, you'll drill into and destroy the screwdriver slot on top of the mix screw. I blunt the end on the sheet metal screw so it doesn't dig into the mix screw and screw it in. It hits the top of the mix screw and as you keep screwing it in, it pushes the plug up and out for you.
The mix screw needs to be removed to properly clean the idle circuit. That may be your problem.