I think the air sensor is ruled out also. Did you verify the EHA function when the car is cold ? Can you check intake vaccum ? At idle, it should be between 16-22 inch Hg. If it is too low, there could be an exhaust clog OR a EGR valve (if your car has one) malfunction. Also what happens to intake vaccum when you press the gas pedal ? Can you check the vaccum that controls the EGR valve ? That valve should be closed at idle, i.e. the vaccum should be lower than 2 inch Hg. Then as you accelerate, at 2000 - 2500 rpm, the vaccum at EGR port should be 5 to 6 inch Hg, enough to open the valve. If this valve does not work like this, idle would be rough and you would also have hesitation during acceleration. These are some other possibilities I can think of. My 87, 260E does not have an EGR valve so would not know its location but should be somewhere around the exhaust manifold since its job is to ricirculate the exhaust.

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Saumil S. Patel