A subscription to EPS, which is free, could make you one of the world's experts on 300E ignition control boxes within minutes. It looks like you're looking for an 86-89 part rather than 90-92 - but lots of superceded part numbers and a VIN split. I too would want to know more about the diagnosis, seems to be an uncommon failure item. Swapping parts with another car is always a good test. Coil is under $70 and seems like a good idea. One of the rebuilders, forget which one, actually requires a new coil or warranty coverage is void.

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