According to international standards, the design of the car's power supply system over 80,000 km of run should not allow exceeding the permissible level of toxic substances in the exhaust gases of the engine.
Based on the foregoing, one should not arbitrarily, in order to improve engine performance, rotate the screw for adjusting the quality of the mixture. If, as a result of the check, it turns out that the level of CO content in the exhaust gases exceeds 0.5 ÷ 1.5%, then only in this case should the appropriate adjustment be made by rotating the specified screw.
A gas analyzer is required for this test. During the test, all of the above conditions must be met. In addition, you should make sure that the exhaust system tract is tight.