When you unplug the air temp sensor, the brain throws the mixture to full rich (12% CO). So you are lean when cold and unplugging the sensor provides some extra fuel, engine runs better.

You should simply check the air temp sensor. There should be 300-400 ohms across its terminals around 60 degrees.

However, the the water temp sensor is a more likely culprit, since it has a larger influence on how much the brain enriches the mixture during warm-up. It is in the front of the intake manifold and should show about 325 ohms with the engine warmed up, much higher with the engine cold.

__________________
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