I was looking through the engine bay for vacuum leaks and noticed that a plug (I think it is the intake air temp sensor) is loose. It's a plug that is attached to cross-over pipe close to the intake runners.
Arthur and everyone, could this have been the cause of my Code 13? It was loose enough that some air could have gotten into the intake.
I reset the code, so we'll see if it comes back.
Thanks for all the help,