E4 part number can mean it is a 84 harness (and probably is) but it is possible that a 85 harness could still have a 'E4' number. I would look at your harness and try to see if there is any evidence that its been removed/replaced. Many times when harnesses are replaced they arent tied down under the dash the way they are at the factory. Id look for that.
A 92-93 EFI harness is the simplest way to go if you are not going to go 'all 86'. You will need to make connections to two connectors on a 92-93 unit - one brown (they can actually be reddish) circular connector that is on the engine compartment side and one green rectangular connector that is under the dash near the computer connector and EEC relay. Using the 92-93 harness (which is identical to FRPP M-12071-C302) allows you to use the FRPP installation manual which spells out everything you need to do. I have this manual and there used to be a copy of it online (bootleg) - but that link is now dead. Maybe someone else here has a good link to an online copy.
One other thing I meant to ask. On your two black '4 pin' connectors - are they really 4 pin or are they 8 pin connectors with only 4 pins loaded? Look carefully into the connector housings.
Paul
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