So what I'm hearing is on the back of the truck is a harness plug (with a litte red slide lock) that goes into the outlet for the trailer (OEM trailer connector). You are taking this outlet off the truck and everything works great until you plug the outlet into the harness. THe trailer is totally unplugged?

 

That is correct. When I plug the red slider right into the tail light everything works great. When the OEM trailer connecter is plugged into the light, and the red slider into the OEM, this is where it gets screwy. However if you cut the red wire for the brake lights on the OEM trailer cable (before the black box) everything works flawlessly until it is reconnected. The trailer is also not connected in any way to the truck.

EDIT:
I went to talk to the trailer guy near my house and it turns out the control box to switch from five to four wires was fried so I replaced that and everything works like a charm again.

 

The power was crossing over and up the system creating the issues. That was where I was going with it but yo beat me to the punch line........LOL


Glad you got it fixed!