The threads I remember relating to misfire and ECU connectors relate to the ignition ECU which is in the engine bay, either on the side of the battery carrier, or on the end of the cylinder head. The tiny pins in the ECU that are supposed to mate with the plug can become loose. Others have opened the ECU to resecure the pins, but a lot of care is needed. Just checking them is a good start.
Most common misfire issues are plug leads, coils or plugs. First question is how old are the plugs?