Anyone have any first hand experience with Iridium spark plugs on the 2.6?

I'm currently going through my new 87 looking at every single part of the car. I've torn out the entire interior and I took the time to replace the 1.5" ehater hose under the dash that usually starts leaking.   Like most other SQs...some of the blend doors for the ducts and boxes have the old disintegrating foam seals. I've been searching for some replacement foam to glue/adhese to the doors and I can't find any good sources. most places want like $20 for a small 6"x12" sheet. most of these door

What does this black bare wire go to? Can you tell me where to attach it?

RockAuto doesn't have these... who does?   I need a full set, new or used i suppose.   Not sure if the year matters, but car is 86 wide body.