[Ieatcamaros]

I am almost certain that it is the flywheel or balancer. If you don't have any friends with mustangs to borrow parts from, I guess it'll be cheaper for you to buy a new balancer and try it first. Then try the flywheel. Can you post pics? If you could post some pics of the balancer and flywheel, we can tell you through pics if something is wrong with them. Then, you would only have to buy one of these.