Note that 2.5L and 2.7L engines come with exhaust manifold/catalytic converter assemblies, while 3.3L engines have conventional 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. Raise the front of the vehicle and securely support it on jackstands, then remove the engine lower splash shield. Disconnect or remove the heated oxygen sensors from the manifold(s), noting that there is an oxygen sensor immediately before and after each catalytic converter. Remove the bolts and the heat shield over the exhaust manifold, and take off the exhaust manifold brace if equipped. If it interferes, remove the dipstick and its tube on 3.3L engines. Detach the fasteners holding the exhaust pipe(s) to the exhaust manifold(s) or catalytic converter(s). Unbolt the exhaust manifold(s) from the cylinder head(s), starting from the ends and moving toward the middle, then slip the manifold(s) off the mounting studs. Carefully inspect the manifold(s) and fasteners for any cracks or damage. Use a scraper to eliminate all old gasket material and carbon deposits from the mating surfaces of the manifold and cylinder head. If the gasket was leaking, check for warpage on the cylinder head mounting surface by placing a straightedge over it and attempting to insert a feeler gauge; if the clearance exceeds the limit, have the manifold resurfaced at an automotive machine shop. Position a new gasket over the cylinder head studs, install the manifold(s), and thread the mounting nuts into place. Tighten the nuts to the specified torque, working from the center out. Reinstall the remaining parts in the reverse order of removal, using new gaskets when connecting the exhaust pipes. Finally, run the engine and check for any exhaust leaks.
