To remove upper intake manifold relieve fuel pressure and disconnect negative terminal from battery source. Remove the air intake duct from the throttle body and drain the engine coolant. If applicable, disconnect the throttle body's cruise control and accelerator cables. If you are replacing the upper intake manifold, you should remove the throttle body; otherwise, leave it in place. Disconnect and label all vacuum hoses, pipes, and lines that may hinder removal. These include those at the distributor and timing belt ends of the engine. Unplug the various fuel, electrical, and emission control connectors, including the volume airflow sensor, control wiring harness, EGR solenoid valve, EVAP purge solenoid valve, knock sensor, CKP sensor, heated oxygen sensor, fuel injector, distributor & EGR connectors. Take off the power steering pump drive belt and the stay. Unbolt the upper intake manifold from the support stays. Remove the bolts/nuts securing the upper intake manifold. Remove the upper intake manifold and gasket with care to not damage the sealing surfaces. Insert clean rags in the water and intake manifold passages at the bottom to prevent debris from getting into the engine when the two intake manifolds are bolted together. Then scrape the old gasket material off both intake manifolds without damaging the surface. Check the flatness of the mating surfaces with a straight edge and feeler gauge and replace or regrind if necessary. To install, remove the rags, vacuum any contamination and install the upper intake manifold with a new gasket, tightening the bolts in three stages. The clamping system installation is just the opposite of the removal and refilling of the cooling system afterwards. To remove the lower intake manifold, relieve the fuel pressure and remove the upper intake manifold, fuel rail and injector assembly. Release and remove the nut on the lower intake manifold. Follow the reverse process of tightening the nuts until they can be removed by hand. Remove the lower intake manifold and place rags in the intake passages of the cylinder head to minimize contamination. Remove any gasket material from the intake manifold and cylinder heads, being careful you do not damage the surfaces. Check the gasket surfaces for warpage and replace or resurface as necessary. After removing any rags, it is important to install the lower intake manifold along with a new gasket on the cylinder head intake passages. Following this, the nuts must be tightened in five stages. After the fuel rail and injector assembly has been installed, reinstall the upper intake manifold with a new gasket in a reverse order of installation and refill the cooling system.