Your 325 should idle as smooth as a Kittie. If does not first check the engine for vacuum leaks (spray starting fluid on all the intake hoses and intake manifold) check for a dead fuel injector of spark plug by removing each plug wire one at a time. (wear rubber gloves or get knocked on you butt) lastly, if all else fails, do a complete compression test. You could have a burnt valve or lifter that is too tight. Don't forget the obvious, bad wires, rotor and plugs. Make sure the plug gap is correct too. Good luck!