misfire

I doubt the intake is cracked unless it is plastic. Possible causes; Faulty spark plug (s), Faulty ignition coil (s), Clogged or faulty fuel injector (s), Intake air leak, Fuel injectors harness is open or shorted, Fuel Injectors circuit poor electrical connection, Ignition coils harness is open or shorted, Ignition coils circuit poor electrical connection, Insufficient cylinders compression, Incorrect fuel pressure...Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. Use some carburetor spray along the intake gasket and spray anywhere there is vacuum to pick up a vacuum leak. You would notice it in the rpm's of the engine. Do this with the engine at idle.