Hello all. New kid on the block HELP!!

I am having a real problem with my car. It is running so rough. i have replaced the intake manifold gasket, the ERG valve and the plugs, but it still is running very rough. I am told i might have a crack in the intake manifold. I have also read that i should replace my intake manifold with a later model on and re place the carburetor. Has anyone got any input for me io don't know where to go next???