To remove the exhaust manifold, first disconnect the negative battery cable from the remote ground terminal. Block the rear wheels, set the parking brake, raise the front of the vehicle, and support it securely on jackstands. Disconnect the downstream oxygen sensor connectors and remove the under-vehicle splash shield if equipped. Unbolt the exhaust pipes at the exhaust manifolds, then lower the vehicle. In the engine compartment, disconnect the oxygen sensor's electrical connector. If removing the rear exhaust manifold, detach the EGR pipe from the top of the manifold; if removing the front manifold, also remove the air filter housing and the engine oil dipstick tube. Remove the exhaust manifold upper heat shield mounting bolts and the heat shields, then detach the manifold from the cylinder head, applying penetrating lubricant to the bolts and threads beforehand. For installation, clean the mating surfaces to eliminate old gasket material and inspect the manifold for distortion and cracks, checking for warpage with a precision straightedge. If necessary, take the manifold to an automotive machine shop for resurfacing. Position the exhaust manifold with a new gasket and lower heat shields, installing the mounting bolts finger tight while ensuring the gaskets are correctly identified by cylinder designation and exhaust port position. Tighten the mounting bolts starting in the middle and working outward in several increments to the specified torque. The remainder of the installation follows the reverse order of removal. Finally, start the engine and check for exhaust leaks between the manifold and cylinder head as well as between the manifold and exhaust pipe.