Greetings Sir or Madam and welcome to JA! I will do my very best to assist you with your problem.
The only thing on the back of the plentum is the tube for the egr valve. If you don't have it removed then you can't get the plentum off. I don't recall any wiring harnesses attached back there.Just the egr tube.
I suspect the egr tube is what is holding you up. Here is a diagram of it. It may be easier to unbolt the egr from the manifold then actually getting this tube off. I am sorry,I am unable to get the diagram to load. I would try removing the egr. You can leave the throttle body attached to it.
You are very welcome and thank you for the accept!
If you have more questions for me just start the post with carguy1 in the beginning and I will get it and help you out!