Im trying to find the right nut for my rwd exhuast manifold on my 4age ( dunno if its different size to the fwd one). I am missing one of the 3 nuts that holds the rest of the exhaust to the manifold. I went to a shop and tried testing all sorts of nuts but all seem to stop at the same point. I reckon this is ebcause the thread is damaged. anyway what size and thread do i need?