Jeff, your description applies to the fuel distributor not the EHA. The EHA is a black plastic chunk on the side of the fuel distributor. It isn't all that expensive and it also is not the problem usually even though its activity is critical for good drivability.
The EHA is a current controlled variable leak to the differential pressure of the fuel distributor. It is the sole vehicle for electronic fuel control. When it isn't functioning the car will hard cold start, have poor cold running characteristics and hesitate on sudden acceleration. The EHA's most common fault is leaking fuel.
One of the ways it fails could explain the original condition here. The device is known to loose its stability. It causes different pressure drops for the amount of current used to control. This causes fluctuating mixtures.
[This message has been edited by stevebfl (edited 09-09-2000).]