Disconnect the negative cable from the battery, then drain the coolant from the radiator. Remove the wires, hoses, cables, and fuel lines at the TBI unit, labeling and disconnecting all wires and hoses connected to the intake manifold, using a screwdriver to remove a stubborn heater hose. If equipped, unbolt the air conditioning compressor and set it aside without disconnecting the hoses. Label and disconnect the spark plug wires from the plugs, then remove the distributor and detach the EGR vacuum line along with the evaporative emission hoses. Remove the valve covers and disconnect the upper radiator and heater hoses. Unbolt the intake manifold and lift it off the engine, prying carefully if it's stuck, ensuring not to pry between the gasket surfaces. Remove all traces of old gasket material and sealant from the manifold and cylinder head mating surfaces, cleaning them with lacquer thinner or acetone, and chase the intake manifold bolt holes in the cylinder head with a tap, using compressed air to clear debris. Check the underside of the rear of the intake manifold for a machined groove that improves oil sealing in later production models. Apply a 3/16-inch bead of RTV sealant to each of the ridges between the heads and cut the intake manifold gaskets where indicated to position the tops behind the pushrods, installing them as marked Right and Left according to the gasket manufacturer's instructions. Hold the gaskets in place by extending the RTV sealant bead up 1/4-inch onto the gasket ends, then install the intake manifold on the engine, hand tightening the bolts and ensuring complete sealing between the block ridges and intake manifold. Following the specified tightening sequence, tighten the manifold bolts in several steps to the required torque, then reinstall the remaining parts in reverse order of removal. Finally, run the engine, adjust the ignition timing, and check for oil and vacuum leaks.