Mine started out as a stumble, then worsened to a stall at idle plus rough running at low RPM. With the OVP and new coil it has gone back to stumbling but not stalling.
Everything thing I have done has made it better for a while but has not seemed to address the basic problem.
My next suspects are the idle control valve and hoses, fuel injectors, and (shudder) the ECU.
My tools are a DMM and a dwell meter - not exactly sophisticated.
You can buy the airflow meter from Bosch separately or the complete pre-calibrated air/throttle plate assembly. There are lots of posts either way. "Airflow meter pot source" is a good one.
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