To state my question in a "catch-all" way...is the problem still an intermittent lack of performance by cylinders 1 and 6? If wiggle tests or visual and resistance tests produce no results, my strategy for suspected harness problems is to cut the suspect wire (at both ends) and run a new (temporary) wire. If the suspect circuit includes a splice or two, then it is necessary to make a mini-harness. Creating a redundant circuit can fix an open circuit type of failure, but removing the suspect wire completely (cut both/all ends) also eliminates possible short-to-ground or short-to-another-circuit. I don't have a magic bullet, but adding a new wire can also provide ready access to a fresh diagnostic checkpoint. DRBIII (drb three) is the name of the dealership scanner from that era that might be most helpful. Classic harness problems on that model are in the valve cover/ firewall area. Also multiple ground connections on passenger side of engine block.