Adjusting the 'carb mixture' screws will make cock all difference to the power your engine makes.
really , why do they have them then ? I'll move your dizzy and fiddle with all your mixture screws next time your going to race up the strip then and see if it goes as well .
carb mixture screws only adjust your idle mixture, you can fiddle with mine as much as you like, Ill just fiddle them back to get it through its MOT. Thats why carburettors have jets, emulsion tubes and whathaveyou so that the mixture through the revs can be altered.