I'm not sure, but I believe the exhaust manifold was changed at some point on YJs due to cracking at two particular flex points. Is this correct? and if so, does anyone know what year? Possibly, the manifold never changed in the YJ years, though I know that there has been manifold issues with the cracking. I only know that I have an upgraded manifold and am trying to find out if is original, changed due to a recall, or changed by a previous owner. This is on my 94 4.0.