I have an 05 GT. It has shorty headers on it already and I am trying to remove the exhaust that is on it now and replace it with a off road X. I coated the bolts that attach the down pipe to the header with PB blaster and went to break the bolts loose. The bolts broke loose but I have noticed that there is a nut on top and it is spinning. I haven't seen this problem anywhere else and need help. How do I get to that but to hold it and prevent it from spinning?

 

I use an impact wrench with a big extension on the bottom and a box wrench on top. One arm will be up in the engine area holding the wrench, the other is on the wrench.

If you take the battery out you can access the passenger side better.

 

You should be able to access the top nut from under the car also.

 

That's correct. It's been so long since I worked on that portion of the car. I think I took out the battery to set the wrench in there and then crawled underneath to grab ahold of it. IDK...

To the OP, don't give up, it's possible.