i doubt its your harness. if anything its your ignition coils. the ignition coils each have a diode on the ground side that lets the DME moniter the spark. did you check the spark pulgs? if they are fould the voltage will be low and the the DME will throw a fault. replacing the wiring should be a last resort. if the fault is always the same two cylinders 6 and 8 then first switch the coils to cylinders 5 and 7 clear the faults and try to get them to happen again. if they move with the coils then thats your problem. if they dont then try moving the spark plugs and see if that moves the fault. if that dosnt work e-mail me and ill get you the wires you need to test. let me know what happens