Evo, I of all people understand your pain on this giving my most recent issue that I myself posted up help for and it ended up being what was in the back of mind the whole time. Problem with getting help on the net is that with us not being in front of the car we can only give suggestions that with hopefully lead to a fix. With that said. Let's be honest. You have pretty much gone over every aspect of this Mustang. So lets look at what you have not fully gone into. 1. Compression numbers are a little on the low side. Not saying this is your issue, but it is there. 2. At this point everyone has tried to get you to look at the engine harness in detail. I personally think this is a great place to start. 3. Only one head got looked at and "fixed". Both should have been pulled and serviced to eliminate any doubt. You have done a great job on your own trying to figure this out. Most people would have givin up a long time ago. I was getting ****ed off at my issue but I would have kicked my own ass if I sold it out of frustration and the new owner fixed it as easily as I did in the long run. To go one step futher. I have an Alldata DYI account I would be willing to give you access to that may help you with this "possible" wiring issue. My car is a 96' however (no COPS) so I dont know how much it would help you. BUT you are more than welcome to it. Stangnet has some of the best folks on here!