Before replacing the upper intake manifold, turn off the fuel pump and remove the negative terminal from the remote ground system. Release and label the vacuum hoses and connectors at the upper intake manifold and throttle body and ETC wiring harness, then remove the air intake duct and air filter housing. Then, further remove the EGR pipe and the upper intake manifold support brackets and then loosen the manifold bolts in the reverse sequence that you tightened them; consequently, you can then take off the manifold and the foam insulator pad. The sealing surfaces and gaskets should be clean and inspected with a view of replacing the bad ones while retaining the serviceable ones. Place and secure the upper intake manifold to the lower intake manifold with the help of bolts, and turn them in the correct order. With regard to the lower intake manifold, at least initially, remove the upper intake manifold; label and disconnect any other hoses that may be in the way. Disconnect fuel rail and injectors, unbolt lower intake manifold as far as possible and then come off in turn, do not use forceful pressure between the manifold and the heads to check the gasket sealing surfaces. Ensure that the sealing surfaces' and gasket condition is okay and replace those that are badly affected. Place the lower intake manifold over the engine and make sure there are proper mating surfaces with the gaskets, install the fuel rail and the injectors. For clearance, leave the fuel rail retaining bolts to be half tightened to facilitate alignment, while tighten all the remaining lower intake manifold bolts in several passes in the sequence recommended above. Lastly, engage the engine turn it on and look for any fuel, vacuum, and coolant leaks.