what is the secret to one that I can not budge! I think the manifold gasket, exhaust, is leaking!
Heat it with a torch if you have one, if not start the car, leave the spark retarded and let it idle for a couple of minutes. This will get the manifold hot in a hurry. You need a wrench that dose not pinch the nut, no pipe wrench or water pump pliers. Wear gloves and remove the nut hot.
Before you heat it up, you can help the loosening process by tapping each flat on the nut with a ball pien hammer. Avoid applying too much torque to the nut or you run the chance of breaking the manifold.
Hope this helps.
Allan from down under.
You can heat the nut and stud up cherry red and then hit just the nut with an ice cube or two to create a rapid cooling rate and it may help t break free.
It might be helpful to indicate which exhaust "pak nut" or manifold "retaining nut" you are attempting to remove - I believe you're getting recommendations for both !