Agree with the Cap'n. If you have a car that starts running rich (or lean for that matter), then adjusting the mixture is not the solution. There is another problem that you need to find and fix.
What I have learned from all the posts on this subject and my own experience is that you make very minor adjustments to the mixture to compensate for component wear, or to re-calibrate the system after a major component has been replaced or repaired.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe