To replace the upper intake manifold, first relieve the fuel system pressure and disconnect the negative battery cable. Remove the engine cover, which may be secured by clips or bolts depending on the model. Next, take off the air filter housing and air intake duct, then disconnect the accelerator cable, vacuum hoses, and other connections from the throttle body. Note that earlier models use an accelerator cable, while later ones utilize an Electronic Throttle Control system. Remove the EVAP hose and transaxle vent hose mounting bracket if present, then clamp off and detach the coolant hoses to the throttle body, being prepared for some coolant spillage. Disconnect the brake booster hose and PCV hoses from the intake manifold, and label the engine harness connectors for reassembly. Unbolt and set aside the Engine Mount Control solenoid, then remove the intake manifold cover. Follow the reverse order of the tightening sequence to remove the bolts and nuts, then take off the manifold and any spacer plate and gaskets if equipped. For installation, clean the mounting surfaces and install a new gasket over the studs on the lower manifold, followed by the spacer and upper intake manifold, tightening the nuts and bolts in sequence to the specified torque. Install the intake manifold cover and tighten the bolts in sequence, then complete the installation in reverse order, checking the coolant level and running the engine to check for leaks. For the lower intake manifold, first remove the upper intake manifold and fuel rails, then detach the two lower intake manifold sections from the 
Cylinder Heads, taking care not to damage the gasket mating surfaces. Use a scraper to remove old gasket material and clean the mating surfaces, then install new gaskets and position the lower manifolds on the cylinder heads, ensuring proper alignment. Tighten the fasteners gradually from the center outwards to avoid warping, then install the upper intake manifold with a new gasket. Complete the installation in reverse order, checking the coolant level and running the engine to check for leaks.