What's the best method of tuning the carb on at 2brl carb. Has idle screw and air mixture screw ( s )

 

You will need a vacuum gauge. Make sure timing, float level, etc are all good first. Warm up the engine and adjust idle speed. Adjust mixture screw for highest possible vacuum. You might have to adjust idle again. Once you have obtained the highest vacuum turn the mixture screw back in just a hair. That should be real close if the jetting is correct.