You are probably running lean for some reason. Does the warm-up regulator hold vacuum on both sides? Do you have any other vacuum leaks? Can you check to see if you in fact have a constant 60% duty cycle? You can always go 1/4 turn richer on the mixture (clockwise) and see if that helps.

Is your timing set correctly? Do you get a good "snap" of timing advance when you blip the throttle?

__________________
Chuck Taylor
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