Models from 2004 and later come with exhaust manifold/catalytic converter assemblies, while those from 2003 and earlier have separate catalytic converters. Begin by disconnecting the cable from the negative terminal of the battery. Apply penetrating oil to the exhaust manifold fasteners and let it soak. For the rear exhaust manifold removal, elevate the front of the vehicle and secure it on jackstands, then take off the engine splash shields. Remove the heated oxygen sensors from the manifold, followed by the bolts and heat shield over the exhaust manifold if applicable. Take off the exhaust manifold brace if present, and then remove the nuts that hold the exhaust pipe to the manifold. Unbolt the manifold from the cylinder head, starting from the ends and moving toward the center, and carefully slip it off the mounting studs. Inspect the manifold and fasteners for any cracks or damage, and use a scraper to eliminate old gasket material and carbon deposits from the mating surfaces. If there was a gasket leak, check for warpage on the cylinder head mounting surface using a straight edge and feeler gauge; if the clearance exceeds the limit, have the manifold resurfaced. Position a new gasket over the cylinder head studs, install the manifold, and thread the mounting nuts into place, tightening them from the center outward. Reinstall all removed parts in reverse order, using new gaskets for the exhaust pipe connections, and finally, run the engine to check for any exhaust leaks.