After we removed the carburetor, the intake manifold gets a final cleaning with carburetor cleaner to loosen the baked-on build-up. Spray the carburetor cleaner on and let it soak. If any spots are stubborn, use the brass brush to get into tight areas. Notice the plug in the PCV valve grommet. Make sure all holes stay plugged throughout the cleaning process. Oh yes, carburetor cleaner will also remove paint. Avoid letting carburetor cleaner sit on the engine paint. At the very least, it will discolor the engine paint.