My brother has a 2006 mustang v6 (4.0) that started having some issues. It would start skipping real bad it was always the back two that would throw a code for skipping. Replace the coil plugs wires. Nothing same thing. So then we replaced the crank sensor on the balancer. Same thing. Changed the ecm. Same thing. I even moved the injectors around to see if the skip would move to another cylinder. Same back two. Is there anyone who can tell me why and what the problem is. And also it’s not a constant skip. It comes at random times but always last about 20 seconds. Doesn’t matter the load the engines on heat fuel nothing. Same thing all the time