Before removing the exhaust manifold, spray the fasteners with a penetrating lubricant, ensuring the engine is cool. For E30 models with S14, M20, or M42 engines, disconnect the negative battery cable and remove necessary components to access the manifold. Remove the mounting bolts, pipe, and heat shields. Disconnect the exhaust pipe at the manifold flange and remove the manifold. Clean all gasket material and replace the gaskets. For E36 models, allow the engine to cool, disconnect the battery, and remove the manifold fasteners. Spray penetrating oil onto the mounting nuts and remove them. Remove the manifolds by lowering them or lifting them out. Replace all gaskets and coat the studs with a high temperature anti-seizing compound. Tighten the fasteners in a crisscross pattern and check for leaks.