If my memory serves me correctly, One goes to the EGR valve (This is the short one), the real long one goes to the solonoid that is at the airpump the other goes to the other emissions solonoid that is the hose to the air pump, I don't remember a 4th. The diagram can be found in a Haynes or Chilton manual or the Probst EFI book.
Hope that helps a little
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