Vacuum pressure

Simple. SET TIMING FIRST. Get idle as close to what you desire RPM, then adjust carb screws alternatively for highest vacuum reading, and if idle goes up or down, readjust RPM. Do this until no improvement is made, and then "end up" with the idle screws "leaning" on the lean side of the peak. That is, just lean them both down a tiny bit the vacuum should not fall off much or at all. Engine must be FULLY warmed. If you have a tach/ dwell, highest vacuum should also coincide with highest idle RPM