Before working on fuel system components, observe the necessary precautions. To remove the engine top cover, prise out the caps and undo the securing nuts, then take off the cover. Next, remove the air cleaner assembly. If applicable, unscrew the nuts and bolts to detach the EGR valve and pipe assembly from both the intake and exhaust manifolds, disconnect the vacuum pipe, and recover the gaskets. Loosen the clip to disconnect the air duct from the adapter or front of the intake manifold, and then loosen the clips to disconnect the vacuum hoses from the intake manifold on the AAT engine. For the AAT engine, unbolt and remove the heat shield from the front of the cylinder head. Using an Allen key, progressively unscrew the bolts securing the intake manifold to the cylinder head, withdraw the manifold, and remove the gasket. For 1Z and AHU engines, undo the screws to remove the adapter from the top of the intake manifold, then unbolt the heat shield and recover the gasket. For ABP, AAT, AEL, and AAS engines, unbolt the air duct adapter and recover the gaskets. Clean the gasket faces of the manifold and cylinder head. Refitting is the reverse of removal, ensuring to fit a new gasket and tighten the bolts to the specified torque.