Disconnect the cable from the negative battery terminal. Remove the intake air duct and the duct support bracket from the top of the engine. Relieve the fuel system pressure and disconnect the fuel line at the quick-connect fitting. Disconnect the wiring from the intake manifold and secure it out of the way. Disconnect the EVAP purge solenoid and its hoses from the back of the manifold, as well as the brake vacuum hose. Label and disconnect the other wiring from the intake manifold, positioning the harnesses aside, and disconnect the PCV hose. Remove the throttle body coolant hose bracket bolts, then remove the throttle body mounting bolts and move the throttle body to the side while leaving the coolant hoses attached. Remove the five upper manifold bolts and a lower intake manifold bolt near the throttle body, then lift off the upper section of the intake manifold. Remove the bolts from the lower intake manifold adapter plate in reverse order of tightening, then take off the lower intake manifold plate. Clean all sealing surfaces thoroughly and replace any damaged lower intake manifold O-rings, using thread locking compound on the lower intake manifold bolts. The remaining installation steps are the reverse of removal, ensuring all fasteners are tightened in the correct sequence to the specified torque values. Finally, reconnect the battery, start the engine, and check carefully for leaks.